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An off-stoichiometric Fe 2 MnSn alloy was prepared by vacuum arc melting and homogenized by vacuum annealing. The structural analysis indicated that the alloy exhibits a D0 19 hexagonal structure. Isothermal magnetization analysis at room temperature showed soft ferromagnetic behavior and exchange magnetic anisotropy. Furthermore, the isofield magnetization study revealed a Curie temperature ( T c ) of 455 K with a second-order magnetic phase transition. A similar trace of the transition point was observed in the differential scanning calorimetric analysis. We estimated a magnetic entropy change ( Δ S M = − 4 J kg - 1 K - 1 ) and refrigerant capacity (RC = 116 J kg - 1 ) from M-T measurements, highlighting its potential for thermomagnetic generators and magnetic refrigerator applications. [ABSTRACT FROM AUTHOR]

Presented work concerns thermally activated 2D materials inducing an electric field in the presence of a magnetic field. The thermomagnetic Nernst effect combines these quantities, and several works reveal results that could be used for validation of the experimental setup before investigations of other structures with potential thermomagnetic effects. The paper shows experimental studies on the thermomagnetic Nernst effect observed in pure nickel samples. The scope of experimental studies covers relationships of the sensitivity of the Nernst coefficient to magnetic field ranging to 1 T and temperature gradient above room temperature. The obtained results were discussed in relation to the referenced works. [ABSTRACT FROM AUTHOR]

Thermomagnetoelectric effect for the dielectric hydrodynamic system is considered. It is established that in a liquid, which is placed in a magnetic field, the temperature gradient can cause a convective mass flow, which leads to the appearance of an electric field in the surrounding space. The distribution of electric potential for various geometric implementations is calculated. A comparison of the obtained effect for normal and superfluid 4He is performed. [ABSTRACT FROM AUTHOR]

Purpose: The adverse effects of temperature on the lubricating properties of nano magnetorheological grease are reduced by applying of a magnetic field. Design/methodology/approach: Nano magnetorheological grease was prepared via a thermal water bath with stirring. The lubricating properties of the grease were investigated at different temperatures. Then the lubricity of the prepared nano magnetorheological grease was investigated under the effect of thermomagnetic coupling. Findings: As the temperature rises, the coefficient of friction of grease lubrication gradually increases, surface wear gradually increases and lubrication performance gradually decreases. Compared with grease, magnetorheological grease has a decreased coefficient of friction and enhanced lubrication effect under the action of a magnetic field at different temperatures. Originality/value: A lubrication method using a magnetic field to reduce the effect of temperature is established, thereby providing new ideas for lubrication design under a wide range of temperature conditions. [ABSTRACT FROM AUTHOR]

Using the method of SQUID magnetometry, the features of the antiferromagnet-ferromagnet thermomagnetic transition in arrays of the nanosized disks of Py/NiCu/Py synthetic antiferromagnets (SAFs) have been investigated. The effective interlayer interaction in individual SAFs "ferromagnet/diluted ferromagnet/ferromagnet" (F2/f/F1) changes from high-temperature antiferromagnetic to low-temperature ferromagnetic upon the transition at the Curie temperature T C f of the interlayer f. Temperature dependence of the magnetic parameters of individual layers and their effect on the features of the thermomagnetic transition are determined. The observed properties are important for the development of temperature-controlled nanoscale SAFs and multilayer nanostructures based on them. [ABSTRACT FROM AUTHOR]

Low-grade thermal energy, either from waste heat or from natural resources, constitutes an enormous energy reserve that remains to be fully harvested. Harvesting low-grade heat is challenging because of the low Carnot efficiency. Among various thermal energy harvesting mechanisms available for capturing low-grade heat (temperature less than 100 °C), the thermomagnetic effect has been found to be quite promising. In this study, we demonstrate a scalable thermomagnetic energy harvester architecture that exhibits 140% higher power density compared to the previously published spring–mass designs. The alternating force required to oscillate the thermomagnetic mass is generated through the interaction between two magnetic forces in opposite directions. We employed numerical modeling to illustrate the behavior of a thermomagnetic device under different operating conditions and to obtain the optimal hot-side and cold-side temperatures for continuous mode operations. A miniaturized thermomagnetic harvester was fabricated and experiments were conducted to systematically evaluate the performance. The prototype was found to exhibit an oscillation frequency of 0.33 Hz, a work output of 0.6 J/kg/cycle, and a power density of 0.2 W/kg of gadolinium under the temperature difference of 60 K. [ABSTRACT FROM AUTHOR]

We report the anomalous Nernst effect (ANE) in bulk La1-xNaxMnO3 (x = 0.02, 0.05, 0.1, and 0.3) samples whose ferromagnetic Curie temperature (TC) is tunable from 251 K to 310 K. The ANE voltage abruptly increases at TC and decreases for T < TC. The maximum value of ANE is achieved for x = 0.1, which shows the highest magnetization value in the series. The temperature dependent ANE (T < TC) is analyzed with the help of dc resistivity and longitudinal thermopower data using Mott's relation, and it is found that the ANE in La1-xNaxMnO3 is dominated by skew scattering. [ABSTRACT FROM AUTHOR]

Transverse magneto-thermoelectric effects were studied in an (In,Fe)Sb ferromagnetic semiconductor thin film under an in-plane magnetic field. We find that the thermal voltage is governed by the planar Nernst effect. We show that the magnetic field intensity dependence, magnetic field direction dependence, and temperature dependence of the transverse Seebeck coefficient can be explained by assuming a Mott relation between the in-plane magneto-transport and magneto-thermoelectric phenomena in (In,Fe)Sb. [ABSTRACT FROM AUTHOR]

In our recent studies, we have developed a thermodynamic biochemical model able to select the resonant frequency of an extremely low frequency electromagnetic field (ELF-EMF) specifically affecting different types of cancer, and we have demonstrated its effects in vitro. In this work, we investigate the cellular response to the ELF electromagnetic wave in three-dimensional (3D) culture models, which mimic the features of tumors in vivo. Cell membrane was modelled as a resistor–capacitor circuit and the specific thermal resonant frequency was calculated and tested on two-dimensional (2D) and three-dimensional (3D) cell cultures of human pancreatic cancer, glioblastoma and breast cancer. Cell proliferation and the transcription of respiratory chain and adenosine triphosphate synthase subunits, as well as uncoupling proteins, were assessed. For the first time, we demonstrate that an ELF-EMF hampers growth and potentiates both the coupled and uncoupled respiration of all analyzed models. Interestingly, the metabolic shift was evident even in the 3D aggregates, making this approach particularly valuable and promising for future application in vivo, in aggressive cancer tissues characterized by resistance to treatments. [ABSTRACT FROM AUTHOR]

Developing new energy generation technologies able to effectively convert low‐grade thermal energy into electricity is an urgent necessity to tackle the continuous surge in energy demand and mitigate climate change. Here, a hybrid device that couples triboelectric and thermomagnetic effects to generate electrical power in the presence of small temperature gradients near room temperature is demonstrated. The thermomagnetic effect allows to induce the periodic and sustained motion of a second‐order ferromagnetic material in temperature gradients below 30 °C. This mechanical motion is then converted into electrical energy using a low‐cost triboelectric nanogenerator (TENG). The applicability of this concept is demonstrated in a broad range of operating temperatures in both the cold (15 to 37 °C) and hot (60 to 90 °C) sides. It is further shown that the electrical power generated by the hybrid TENG is more than 35× higher than that obtained by a conventional thermomagnetic generator driven by magnetic induction. The obtained results show that this implementation is a feasible thermal energy conversion technology, further expanding the applicability of triboelectricity into the realm of room temperature thermal harvesting. [ABSTRACT FROM AUTHOR]

Recently, the low frequency thermomagnetic effects on cancer cells have been analysed, both theoretically and experimentally. They have been explained by introducing an equilibrium thermodynamic approach. But, in this context, two related open problems have been highlighted: (1) Does there exist a magnetic interaction or do there exist any other processes? (2) Do there exist also thermal effects? Here, we introduce a non-equilibrium thermodynamic approach in order to address an answer to these questions. The results obtained point out that: (a) the effect produced by the electromagnetic wave is just a consequence of the interaction of the magnetic component of the electromagnetic wave with the biological matter; (b) the interaction of the electromagnetic wave causes also thermal effects, but related to heat transfer, even if there have been applied low frequency electromagnetic waves; (c) the presence of the magnetic field generates a symmetry breaking in the Onsager's coefficients, with a related perturbation of the cancer stationary state. [ABSTRACT FROM AUTHOR]

A method to compare the thermal to magnetic transduction efficiencies of different thermomagnetic systems was developed. The efficiencies of operating about a spin reorientation transition and the alternative ferromagnetic to paramagnetic transformation at the Curie point were directly compared. A case study was performed comparing Gd operating about its spin reorientation temperature and its Curie point. Additionally, a case study on NdCo5 operating about its spin reorientation temperature using experimentally derived values of the materials' temperature dependent magnetic properties was conducted. Analysis suggests that choosing the appropriate material and operating it about its transition produces considerable efficiencies (∼22%) as well as large harvestable energy densities (∼2.6MJ/m³), which is an order of magnitude larger than Gd single domains operating about their Curie point (∼100 kJ/m³). [ABSTRACT FROM AUTHOR]

Magneto-optical imaging films (MOIFs) were used for the study of magnetic stray field distributions above topographically and thermomagnetically patterned permanent magnet films and other miniature elements that could be used in magnetic micro-systems. Calibrated external bias fields were applied to the samples in situ to simplify the graduation procedure, to expand the measurement range and to minimize the measurement errors. Both uniaxial and planar MOIF were used to make quantitative measurements. A scheme for the fast reconstruction of magnetic serial sections of nonuniform field profiles is proposed. The usefulness of biased MOIF imaging is illustrated by a number of specific examples, such as mechanical hole-drilling adapted to the case of magnetic analysis, dynamic range expansion beyond the limits set by MOIF saturation, rendering surface magnetic flux variations at the microscale and in the presence of strong background. [ABSTRACT FROM AUTHOR]

In magnetism literature, usually the applied or external field H0 is taken to present the results of an investigation. But for certain purposes, it is advantageous to work with the internal magnetic field H that occurs inside a magnetic body. It is well-known that the susceptibility of the material and the demagnetization effect, given by the geometry of a body, link the two usually different fields under consideration. If a probe is a long needle with the external magnetic field and the magnetization in the probe parallel to the axis of the slender body, the two fields are identical. But when building thermomagnetic machines, other demands may require also other shapes (porous materials, particle beds, wavy structures, etc.) of the magnetized material and then a correct distinction of these fields becomes important and in some cases also laborious if one of them must be theoretically determined from the other. This article shows how--from a theoretical point of view--the most important physical properties of thermomagnetism/magnetocalorics, namely, the adiabatic entropy change, the effective specific heat capacity, and the adiabatic temperature change must be transformed. Furthermore, this theory reveals the invariants of magnetocalorics, which are combinations of these three most important properties. [ABSTRACT FROM AUTHOR]

The impact of B substitution in Ni50Mn35In15-xBx Heusler alloys on the structural, magnetic, transport, and parameters of the magnetocaloric effect (MCE) has been studied by means of room-temperature X-ray diffraction and thermomagnetic measurements (in magnetic fields (H) up to 5 T, and in the temperature interval 5-400 K). Direct adiabatic temperature change (DTAD) measurements have been carried out for an applied magnetic field change of 1.8 T. The transition temperatures (T-x) phase diagram has been constructed for H=0.005 T. The MCE parameters were found to be comparable to those observed in other MCE materials such as Ni50Mn34.8In14.2B and Ni50Mn35In14X (X=In, Al, and Ge) Heusler alloys. The maximum absolute value of ΔTAD=2.5K was observed at the magnetostructural transition for Ni50Mn35In14.5B0.5. [ABSTRACT FROM AUTHOR]

Ferromagnetic Fe-Ni-Co-Al-(Ta,Nb)-B microwires with diameters from 170 lm to 50lm, which possess both superelastic and good magnetic properties, have been prepared by rapid quenching from the melt using the in rotating water spinning technique followed by cold-drawing and ageing. The cold-drawing and annealing processes lead to the initialization of premartensitic phases as confirmed by the X-ray diffraction and scanning transmission electron microscopic investigations, more significantly in the 50 μm cold-drawn microwires. An increase in the coercive field and in the saturation magnetization has been obtained by annealing, more importantly in the case of Nb-containing alloy. Ageing by thermal or current annealing led to the initialization of the superelastic effect. High values of strain of up to 1.8%, very good repeatability under successive loading, and values of superelastic effect of up to 1.2% have been achieved. The structural analysis coupled with the stress-strain data suggests that these materials annealed at 800 °C have superelastic potential at reduced ageing times. The magnetic behavior was found to be easily tailored through both thermal and thermomagnetic treatments with changes in the magnetic parameters which can be contactless detected. The results are important for future applications where both mechanical and magnetic properties matter, i.e., sensing/actuating systems. [ABSTRACT FROM AUTHOR]

Measurements of the adiabatic temperature change (ΔT) and the specific heat transfer (ΔQ) of Ni2.18Mn0.82Ga Heusler alloy were taken in order to quantify the direct giant magnetocaloric effect of the alloy when it is in the vicinity of magneto-structural phase transition (PT) from paramagnetic austenite to ferromagnetic martensite, and their results are presented. A new vacuum calorimeter was used to simultaneously measure ΔT and ΔQ of magnetocaloric materials with a Bitter coil magnet in fields of up to H=140 kOe. Other thermomagnetic properties of this alloy were investigated using standard differential scanning calorimetry and PPMS equipment. The maximal values of magnetocaloric effect in H=140 kOe were found to be ΔT=8.4K at initial temperature 340K and ΔQ=4900 J/kg at 343 K. Using this direct method, we show that the alloy indeed demonstrates the largest value of ΔQ as compared with previously published results for direct measurements of magnetocaloric materials, even though at 140 kOe the magnetic field-induced magnetostructural PT is still not complete. [ABSTRACT FROM AUTHOR]

We use a three-flavor Nambu–Jona-Lasinio model to study the thermodynamics of strange quark matter under a strong magnetic field. The model Lagrangian features flavor SU(3) four-quark interactions and six-quark interactions that break the U A (1) symmetry. We incorporate thermomagnetic effects in the four-quark coupling by fitting lattice results for the average of u and d quark condensates close to the pseudocritical temperature. We compute the pressure at the mean field level and obtain the magnetization of quark matter. We adopt the recently proposed vacuum magnetic regularization (VMR) scheme, in that divergent quark mass independent contributions are not subtracted, thereby avoiding unphysical results for the magnetization. We devote special attention to the renormalized magnetization, a projected quantity that allows for direct comparisons with lattice QCD simulations. Our results are in very good agreement with lattice data indicating a paramagnetic behavior for quark matter. [ABSTRACT FROM AUTHOR]

A nonlinear study is made to find the influence of transverse anisotropy on the onset of thermomagnetic convection in a homogeneous and rotating porous medium. The medium is filled with a magnetic fluid and is subjected to centrifugal force with alternating directions. Unconditional nonlinear stability bounds are found by exploiting the variational principles. Effects of various parameters on the stability threshold are discussed. The overpredicting nature of the linear theory is demonstrated by isolating the subcritical region which cannot be obtained a priori. [ABSTRACT FROM AUTHOR]

The surface current density of charge carriers in two-dimensional doubly periodic n-type semiconductor superlattices in an external magnetic field in the presence of temperature gradient has been calculated in the single-electron approximation. The magnetic field was assumed to be permanent, homogeneous, and oriented perpendicular to the electron-gas plane. A joint solution of the Schrödinger equation and kinetic Boltzmann equation showed that the dependences of the surface density of transverse current on temperature and temperature-gradient magnitude are significantly nonlinear and contain portions with negative transverse differential conductivity. The dependence of the relaxation time on the electron quasi-momentum is phenomenologically taken into account in the model via the dispersion relation for carriers in magnetic subbands. [ABSTRACT FROM AUTHOR]

The benefit of transformer oil seeded with magnetic nanoparticles (forming a transformer oil-based ferrofluid) is numerically studied in an axisymmetric model of 40 kVA transformer. The maximum temperature in the system is decreased by 2.2 °C when using ferrofluid instead of transformer oil. This effect is mainly due to the magnetic body force, which modifies the convective flow in the system and enhances heat transfer. The leakage magnetic field is highly localized and limits the effect of thermomagnetic convection. Varying the geometry of the primary coil assembly allows to increase this effect and to decrease the maximum temperature. [ABSTRACT FROM AUTHOR]

Most spin caloritronics research utilizes thin films on substrates with an in-plane heat flow, where an unintended out-of-plane thermal gradient may develop by heat dissipation through the substrate. In systems exploiting metallic ferromagnets to generate or detect spin currents, such out-of-plane thermal gradients might confuse the signal via undesirable thermomagnetic effects, such as the anomalous Nernst effect. Here, we report direct measurement of the spin current created by the spin Nernst effect in platinum, using ferromagnetic metal contacts as spin accumulation detectors. By comparing the voltage measured transverse and longitudinal to the thermal gradient, we find that the device geometry is crucial in all-metallic systems. Exploiting the orthogonality in the angular dependence on the external magnetic field of the transversely measured voltage, we quantitatively separate the spin Nernst signal from the parasitic anomalous Nernst voltage, which are of the same order of magnitude. As a result, we estimate the spin Nernst angle of platinum to be comparable to the spin Hall angle in magnitude with an opposite sign. [ABSTRACT FROM AUTHOR]

Some of the advances made in the literature to understand the phase transitions of quark matter in the presence of strong magnetic field and finite temperature (zero quark chemical potential) are reviewed. We start by discussing the physics behind the Magnetic catalysis (MC) at zero/finite temperature and then focus on the lattice predictions for inverse magnetic catalysis (IMC) at high temperature and strong magnetic fields. Possible explanations for the IMC are covered, as well. Finally, we discuss recent efforts to modify QCD (quantum chromodynamics) effective models to reproduce the IMC observed on the lattice simulations. We emphasize the fact that applying thermomagnetic effects on the coupling constant of the NJL model significantly improve the effectiveness of the NJL model to obtain a reasonable physical description of hot and magnetized quark matter being in agreement with lattice results. [ABSTRACT FROM AUTHOR]

Magnetic properties of compacted Sm0.1Ca0.9MnO3 particles with 25 and 60 nm average sizes have been investigated. Particular attention has been paid to Griffiths-like features at temperatures above magnetic transition temperature TC and to the system glassiness at low temperatures. Griffiths-like features in inverse magnetic susceptibility of Sm0.1Ca0.9MnO3 nanoparticles have been linked to the presence of short range ferromagnetically correlated spin clusters above TC. Glassy behavior has been revealed in temperature and frequency dependence of ac-susceptibility, temperature and field dependence of thermoremanent and isothermoremanent magnetization, and time decay of the remanent magnetization. Experiments revealed the major impact of the glassy component on magnetic properties of investigated nanoparticles. The magnetic relaxation associated with glassy features was found to be much more pronounced in smaller particles, where a formation of collective state in an ensemble of phase separated nanoparticles may take place. Thermomagnetic irreversibility found in Sm0.1Ca0.9MnO3 nanoparticles has been linked to martensitic strain effects. [ABSTRACT FROM AUTHOR]

Understanding the locus of fluid flow along thrust and splay faults is important to understand the hydraulic properties of accretionary systems and fault mechanics. Here, we use rock magnetic techniques in combination with backscattered electron imaging to depict the locus of enhanced magnetic mineral alteration within the Pāpaku fault, an active splay fault of the subduction interface at the northern Hikurangi Margin. The Pāpaku fault was cored at Site U1518 during Expedition 375 of the International Ocean Discovery Program and we report room temperature magnetic parameters, complemented by first‐order reversal and thermomagnetic curves in the depth interval 250–400 m below seafloor (mbsf). The ∼60‐m wide Pāpaku fault zone comprises two main slip zones, referred to as the upper main brittle (304–321 mbsf) and lower subsidiary (351–361 mbsf) fault zones, and an intervening zoned, termed the lower ductile deformation zone. Two narrow zones, at the top of the main brittle fault zone, and one in a sand‐rich interval above the subsidiary fault zone, experienced enhanced magnetic mineral diagenesis, which resulted in the recrystallization of ferrimagnetic greigite to paramagnetic pyrite. We propose that secondary magnetic mineral diagenesis was driven by anaerobic methane oxidation within these intervals, which occurs in the presence of methane and sulfate. We relate the observed changes to the fault parallel transport of fluids which is restricted to two damage zones. Overlying compacted and clay‐rich sediments likely act as a barrier to upward advective flow through the fault zone and into the hanging wall. Key Points: We report the results of rock magnetic properties and backscattered electron investigations in a profile through a subduction splay faultEnhanced magnetic mineral diagenesis in two slip zones resulted in the neoformation of iron‐sulfide mineralsWe suggest that the accumulation and fault parallel transport of reactants in fracture zones allowed anaerobic methane oxidation to occur [ABSTRACT FROM AUTHOR]

The spin crossover salt [Fe(bpp)2](isonicNO)2⋅ 2.4 H2O (1⋅2.4 H2O) (bpp=2,6‐bis(pyrazol‐3‐yl)pyridine; isonicNO=isonicotinate N‐oxide anion) exhibits a very abrupt spin crossover at T1/2=274.4 K. This triggers a supramolecular linkage (H‐bond) isomerization that responds reversibly towards light irradiation or temperature change. Isotopic effects in the thermomagnetic behavior reveal the importance of hydrogen bonds in defining the magnetic state. Further, the title compound can be reversibly dehydrated to afford 1, a material that also exhibits spin crossover coupled to H‐bond isomerization, leading to strong kinetic effects in the thermomagnetic properties. [ABSTRACT FROM AUTHOR]

Variably serpentinized peridotites from the Zedang ophiolite in southern Tibet were magnetically and petrologically examined to understand the serpentinization process and evaluate the origin of magnetic anomalies in ultramafic‐hosted tectonic settings. Magnetite occurs in the serpentine and brucite veins and is identified as the dominant magnetic carrier by thermomagnetic and petrological analyses. The magnetic susceptibility increases rapidly from <0.001 to ~0.02 SI for the <50% serpentinized samples followed by nearly constant values of 0.02–0.03 SI above 50% serpentinization. This transition corresponds with the formation of Fe‐poor serpentine mesh (2–3 wt% FeO) and magnetite in the early stages and the replacement of mesh center olivine by Fe‐rich serpentine (4–5 wt% FeO) without magnetite in the late stages. Brucite veins occur in the 50–70% serpentinized samples and indicate serpentinization temperatures from ~250 to <100°C. The serpentinization may initiate at an oceanic spreading ridge center under high temperatures (>250–300°C) to produce magnetite and subsequently continue at lower temperatures (<200–250°C) in near‐seafloor settings and limit the magnetite formation, possibly associated with ophiolite emplacement. These serpentinized peridotites have higher magnetization intensities (average 2.26 Am−1) than dolerite dykes and basaltic volcanics (mostly <1 A m−1) in the area and should be the major source of aeromagnetic highs in the south Tibetan ophiolite belt. Key Points: Variably serpentinized peridotites from the Zedang ophiolite in southern Tibet were magnetically and mineralogically examinedWe observed that magnetite formation is limited above ~50% serpentinization in the Zedang ophioliteThe serpentinization may start at >250–300°C at an oceanic spreading ridge center and continue at <200–250°C in near‐seafloor settings [ABSTRACT FROM AUTHOR]

The modern designs of magnetic field transducers (MFTs) based on nanostructures with the spin-tunnel magnetoresistive effect (STMR) and the main areas of their application are considered. The results of an experimental study of two constructive versions of magnetic field transducers with an even and odd output characteristic are presented. The sensitivity of the fabricated MFT model based on the STMR effect with an even output characteristic is 0.54 mV/(V Oe) in the range of a magnetic field with the intensity ranging from 0 to 40 Oe. The results of dependency conversion are presented. R(H) nanostructures with the STMR effect by thermomagnetic treatment to reduce hysteresis and increase linearity in the working range of the magnetic field. The sensitivity of the fabricated MFT model based on the STMR effect with an odd output characteristic is 5.4 mV/(V Oe) in the range of a magnetic field with a strength of ±1 Oe. In conclusion, promising directions of the development of magnetic field converter (MFC) structures based on nanostructures with the STMR effect are described. [ABSTRACT FROM AUTHOR]

Recent studies have pointed out that first-order magnetic transitions can be affected by defects. It however remains unclear which precise microstructural features are involved and how to pragmatically control their formation. Here, we show that a genuine technical parameter such as the compaction pressure employed prior to the sintering can induce subtle differences on magnetization data and yet correspond to a large evolution of the magnetocaloric performances in MnFe 0.95 P 0.575 Si 0.36 B 0.065 compounds prepared by powder metallurgy, resulting in an enhancement of the isothermal entropy change (Δ S) in 1 T up to ∼40 %. This outcome is unexpected as Δ S normalized per mass should not be affected by what is at first glance a matter of compaction or density. Our detailed structural and microstructural investigations indicate that the sharpening of the transition for the highest compaction pressures originate from different distributions of the secondary phase at the grain boundaries. This work not only bring into light an interesting fundamental question how microstructural details can affect the development of a magnetic transition, it has also important practical consequences to ensure a reproducibility of large magnetocaloric or thermomagnetic effects in MnFe(P,Si,B) materials for possible applications. [Display omitted] • Magnetocaloric performances of MnFe(P,Si,B) increase with higher green compaction. • Final density not affected by green pressure with common 24 h high temperature sintering. • Increase in ΔS is not related to secondary phase content but rather to its distribution. [ABSTRACT FROM AUTHOR]

The anomalous Nernst effect (ANE), one of the thermomagnetic effects studied for a long time, has recently attracted renewed attention. The ANE, which originates from fictitious fields in momentum space, is essential for clarifying the interplay among heat, spin, and charge in magnets. Moreover, compared to the Seebeck effect, it has various benefits for application to high-efficiency energy-harvesting devices as it may provide much more simple lateral structure, higher flexibility, and much lower production cost. In this review, we discuss various topics related to the methods to modulate the ANE for its thermoelectric applications. In addition, we review strategies to design materials to obtain large ANE including Weyl magnets and thermoelectric devices for effectively utilizing the ANE. [ABSTRACT FROM AUTHOR]

We studied the thermomagnetic power S ii (B) and Nernst–Ettingshausen effect S ij (B) in inclination bicrystals of Bi and 3D topological insulator Bi 1−x Sb x (0.04 < x ≤ 0.12) with superconducting nano-width interfaces (T c ≤ 21 K). High values of thermomagnetic effects in small disorientation angle (SDA) bicrystals far exceeding values in single-crystalline samples were found. It was established that S ii (B) linearly increases in high fields without saturation and change the sign from negative in positive in bicrystals of 3D Dirac point forming (x ∼ 0.04), specifying the signature of 3D topological semimetal. Contrarily, S ii (B) in LDA bicrystals with 0.06 ≤ x ≤ 0.12 undergoes saturation or increases smoothly, the Landau level index depends linearly on 1/ B n , and extrapolate to – 0.5 if 1/ B n → 0, what is typical for the 3D topological insulators. Two new quantum oscillation harmonics are reviled in high fields; they characterize different densities of electronic states and different levels of disorder at LDA and SDA interfaces. • The thermomagnetic effects in small inclination bicrystals with nano-width superconducting interfaces are considerably higher than in single crystals and large disorientation angle samples of Bi and Bi 1−x Sb x (0.04 ≤ x ≤ 0.12) alloys. • The inclination bicrystals of 3D Dirac point forming (x ∼ 0.04) show features of thermomagnetic transport characteristic of 3D topological semimetal. • The high magnetic field dependences of thermomagnetic power in Bi 1−x Sb x (0.06 ≤ x ≤ 0.12) bicrystals are typical for 3D topological insulators with massless Dirac fermions. • Two new quantum oscillation harmonics are reviled in high fields; they characterize different densities of electronic states and different levels of disorder at small and large inclination interfaces. [ABSTRACT FROM AUTHOR]

Highlights • Ti fully dissolves in NiMnGa-based single phase structure. • Gd addition promotes dual-phase microstructure in the NiMnGa-based alloy. • Ti for Ga substitution leads to the decrease of the martensitic transition temperature. • Gd shifts the martensitic transition temperature to the room temperature regime. • Ti and Gd improved the mechanical properties of the NiMnGa-based alloy. Abstract The present study is focused on the influence of Ti and Gd doping at the Ga site on the microstructure, magnetic and mechanical properties of the polycrystalline Ni 50 Mn 25 Ga 20-x Z x (x = 0 or 5, Z = Gd, Ti) magnetic shape memory alloys. Microstructure investigations show that reference Ni 50 Mn 25 Ga 25 and Ti-doped alloys, both in the as-cast and annealed state, are single phase materials, whereas Gd-doped sample reveals dendritic dual-phase structure with substantial distinction between Gd-rich and Gd-poor regions. Thermomagnetic measurements expose reversible martensitic transition in the Ni 50 Mn 25 Ga 25 and Ni 50 Mn 25 Ga 20 Ti 5 alloys, where Ti addition to NiMnGa composition leads to the decrease of phase transformation temperature from T M = 193 K for reference sample to T M = 172.5 K for Ti-doped material. Furthermore, the Ni 50 Mn 25 Ga 20 Gd 5 alloy does not experience fully martensitic transition. Temperatures of magnetic transformation also varies with chemical composition and equals to 379 K, 318 K and 370 K for the annealed Ni 50 Mn 25 Ga 25 , Ni 50 Mn 25 Ga 20 Ti 5 and Ni 50 Mn 25 Ga 20 Gd 5 alloy, respectively. Mechanical properties investigation based on the nanoindentation measurements shows beneficial influence of doping elements on material hardness. In addition, planar distributions of hardness allow to deconvolute mechanical properties of each individual phase of the Ni 50 Mn 25 Ga 20 Gd 5 alloy. [ABSTRACT FROM AUTHOR]

Abstract It is usually claimed that structural and magnetic transitions should coincide to improve the total entropy change. Here we show that overlapping structural and magnetic transitions can compete with each other, which gives rise to some signature of the competition misinterpreted as an experimental artifact of the measurements as observed in Ni 49+x Mn 36-x In 15 (nominally x = 0, 0.5, 1.0, 1.5 and 2.0) investigated in this work. Their various magnetic phase transitions show a low temperature conventional magnetocaloric effect (MCE), an inverse MCE followed by another high temperature conventional MCE. For concurrent phase transitions with their respective transition temperatures close to one another, an observed spike embedded in the high temperature conventional MCE region is found arising from the martensitic transformation. We show that a crossover of the magnetic field dependence of the transition temperatures is obtained for concurrent phase transitions occurring in a narrow temperature range. As an evidence of the complexity of overlapping phase transitions, a recently proposed quantitative method for determining the order of phase transition is applied to this compositional series, showing its applicability even to cases when first- and second-order phase transitions occur in a narrow temperature range. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Thermomagnetic convection is a controlling phenomenon for heat-transfer in ferrofluids. It depends upon the magnetic field gradients, variation in magnetic susceptibility, particle concentration and temperature gradients. This article presents the effect of these parameters on cooling of a current carrying micro-wire in ferrofluid with a focus on magnetophoresis effects. A two-phase Euler-Euler model is developed. The predictions of this model are compared with experimental results and predictions from a single-phase ferrofluid model. For ferrofluid with volume fraction of φ = 0.02, the predicted average wire temperature from the Euler-Euler two-phase model is approximately 1 K lower than the measured wire temperature,while the single phase model is 5 K higher. Under identical magnetic field and heat flux conditions, variations in the particle concentration are found to have a non-negligible effect on thermomagnetic convective cooling. The maximum temperature of the wire for φ = 0.01 ferrofluid is significantly increased by 10 K and greater enhancement to cooling is observed in the case of φ = 0.04, where the inception of thermomagnetic cooling is advanced. Correspondingly, significantly different thermal and velocity fields are observed for different volume fractions. The simulations show different regimes of heat transfer. During the first few hundred milliseconds after applying electrical current, a thin boundary layer develops near the wire surface and the colder region is thermally stratified. At larger time, dispersion of ferro-particles between colder and hotter regions produces concentration gradients which affect the thermal and velocity fields. Eddies generated by thermomagnetic convection are found to form at the bottom of the vertical wire and retain their structure as they are convected upwards by natural convection. The particle concentration at the wire surface (φ w s) varies from 0.0188 to 0.0260 for an initial volume fraction (φ) of 0.02. This variation disturbs the thermal boundary layer and generates thermal vortices around the heated wire that differ from single-phase model predictions. • Validation of Two-Phase and Single-phase thermomagnetic model with experiment. • Variation in local concentration of ferroparticles around heated Cu-wire. • Plume-like flow structures for the higher concentration ferrofluid. • Continuous rising of thermal cells adjacent to the vertical wire. [ABSTRACT FROM AUTHOR]

Magnetic properties and microstructure of directly quenched Nd9.5Fe72.5-yTi2.5Zr0.5CryB15-xCx (x =0-1; y=0-3) magnets with a diameter of 1.1 mm and a length of 15 mm have been investigated. The thermomagnetic analysis show that the bulk magnets with x⩽0.5 and y=0-3 mainly consist of magnetically hard 2:14:1 phase. Besides, a slight substitution of C for B and Cr for Fe in Nd9.5Fe72.5-yTi2.5Zr0.5B15 can effectively refine the grain size of the bulk magnet with larger diameter, resulting in the remarkable enhancement of the magnetic properties. The optimal magnetic properties of Br=5.9 kG, iHc=8.2 kOe, and (BH)max=7.2 MGOe could be attained in Nd9.5Fe71.5-yTi2.5Zr0.5Cr1B14.5C0.5 magnet. [ABSTRACT FROM AUTHOR]

The adiabatic temperature change (ATad) in Ni45 Mn43CoSn11 has been measured by a direct method in magnetic field changes up to 14 T. Large reversible magnetocaloric effects resulting in ΔTad of about = -11 and 5 K have been observed for magnetic field changes of 14 T at the magnetostructural (TA ~ 260 K) and magnetic transitions (TC ~ 320 K), respectively. The impact of the thermomagnetic history on ΔTad at high magnetic fields has been reported. The significant observed changes in the relaxation time of ΔTad, depending on the type of the phase transitions, magnetization, and demagnetization cycle are discussed. [ABSTRACT FROM AUTHOR]

We conducted an absolute palaeointensity (API) survey on Ethiopian volcanics from Early Oligocene (Belessa section) and Middle Miocene (Debre Sina section). After a careful selection based on the reversibility of high-field thermomagnetic curves from samples yielding unambiguous palaeodirections, we restricted our analysis to five (resp. six) cooling units from Belessa (resp. Debre Sina), submitted to both Thellier and Wilson-style experiments. X-ray diffraction measurements and microscopical observations under reflected light gave us good confidence in the reliability of the remanence carriers of the Belessa basalts, with pseudo-brookite exsolutions in titanomagnetite (TM) grains, synonymous of an advanced stage of high-temperature (i.e. deuteric) oxidation. In contrast, the Debre Sina trachybasalts may have been submitted to low-temperature (i.e. post-consolidation) alteration featured by granulation of TM grains and leading to a higher dispersion of API estimates. Compared to the 'world palaeointensity database', the lower dipole moment found in Ethiopia for the Early Oligocene (30 ± 8 ZAm2) than the Middle Miocene (65 ± 20 ZAm2) is compatible with a global increase of dipole strength from 30 Ma to present, and also suggestive of a dipole low during the Oligocene. This observation must however be treated with caution because of the over-representation of Plio-Pleistocene determinations in the global database and the partial correlation between dipole strength and number of palaeointensity determinations. [ABSTRACT FROM AUTHOR]

The current stimulated atomic diffusion in YBa2Cu3O7–δ superconducting bridges is investigated. A superconductor to insulator transition can be induced by the current controlled electromigration process, whereas the partial recovery of the superconducting state can be achieved by inverting the polarity of the bias. Interestingly, the temperature dependence of the current density JEM(T), above which atomic migration takes place, intersects the critical current density Jc(T) at certain temperature T*. Therefore, for T < T*, the current-induced dissipative state cannot be accessed without leading to irreversible modifications of the material properties. This phenomenon could also lead to the local deterioration of high critical temperature superconducting films abruptly penetrated by thermomagnetic instabilities. [ABSTRACT FROM AUTHOR]

Abstract The use of pyrrhotite-containing aggregate in concrete has led to the premature deterioration of building foundations in Connecticut (U.S.A.). Pyrrhotite is a highly reactive iron-sulfide mineral that can initiate internal sulfate attack in concrete structures, because it serves as a source of sulfate ions for secondary minerals. Associated increases in mineral volume can lead to spalling, cracking and a loss of structural integrity. Since pyrrhotite is a strongly ferrimagnetic mineral with a Curie-temperature of 325 °C and several diagnostic phase transitions, we measured the variation of magnetic susceptibility between room-temperature and 700 °C. Such a thermomagnetic measurement serves as a rapid and sensitive semi-quantitative indicator of pyrrhotite in aggregate or concrete samples. In combination with measurements of total sulfur concentrations, pyrrhotite concentrations as low as 0.1% can be detected. The analysis can aid in the quantification of risk of internal sulfur attack due to the presence of pyrrhotite. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Coupled device for simultaneous cooling and electricity harvesting using waste heat. • Cooling of heat load by 70 °C and voltage of upto 10 V/cycle and 15 mA current/cycle. • Thermomagnetic response combined with Electromagnetic induction for first time. • Simulation and optimization of device parameters performed for effective voltage output. Abstract Waste heat is an unavoidable and undesirable product of a huge number of industrially important processes. Cooling of such a heat load is of high interest. We developed a novel hybrid thermomagnetic oscillator (TMO) for cooling of the heat load as well as electricity harvesting. A bulk alloy, with a composition of (MnNiSi) 0.7 (Fe 2 Ge) 0.3 and Curie temperature of 144 °C, was used as the thermomagnetic material. Heat load cooling by mechanical oscillation between the load and the sink by up to 70 °C was achieved. Voltage of up to 10 V/cycle and a current of 15 mA was generated by the mechanical oscillation of this alloy and a coupled permanent magnet through solenoid type Cu coils. This energy was stored in a capacitor and used to light up a LED. The thermomagnetic material transferred heat from the heat load to the heat sink. A moving mesh based numerical model was developed to determine the role of various parameters on the performance. Our simulations are in good agreement with our experimental findings. Superior device performance can be achieved by higher magnetic field strength, sample mass, thermal conductivity of the sample, and optimum device height. [ABSTRACT FROM AUTHOR]

Abstract This article investigates the history of long-term radial and circumferential creep strains and radial displacement for a three-phase nano-composite exposed to an internal pressure and placed uniform temperature and magnetic field. Three-phase nano-composite made of single-walled carbon. The results in this paper were achieved by presuming a non-linear viscoelasticity, based on Shapery's integral model, classical laminate theory, Prandtl-Reuss's relation and Mendelson's approximation method. The distribution of the radial creep strain, circumferential creep strain and radial displacement in two states of with and without magnetic field and three temperature conditions for two lay-ups [0/45/0/45] and [0/90/0/90] described for 10 years. It has been found that the values of creep strain and radial displacement in magnetic field are lower than without a magnetic field, for two lay-ups. [ABSTRACT FROM AUTHOR]

Hysteresis, thermomagnetic and low-temperature magnetic experiments on particle-size fractioned samples from the Chinese Loess Plateau (CLP) can be used to better characterize the magnetic mineralogy and magnetic granulometry of Chinese loess/palaeosols. However, a systematic study of the grain-size-dependent magnetic mineralogy of the Central Asian loess deposits has not been undertaken. In this paper, four size fractions of 17 loess and palaeosol samples from Central Asia and the CLP were subjected to aforementioned rock magnetic measurements. Our findings are as follows: (1) In Central Asia, the fractionated samples from loess and palaeosol couplets exhibit no obvious differences in their magnetic mineralogy due to weak pedogenesis. (2) Thermomagnetic analyses suggest that the content of maghemite in the clay fraction of palaeosols from the CLP is one or two orders of magnitude larger than that of the loess samples from the CLP and Central Asia. This result does not support the view that maghemite in the loess/palaeosol sequences of the CLP originated mainly from eolian sources. (3) Both hysteresis and low-temperature magnetic experiments demonstrate that detrital ferrimagnetic grains are mostly enriched in the 20–75 μm fraction of loess/palaeosols from Central Asia and the CLP. The relative paucity of coarser magnetic grains in the >75 μm fractions indicates that a positive correlation does not always exist between the magnetic concentration parameters and the sedimentological particle size in Chinese loess deposits. (4) The regional variations in the magnetic properties of the 20–75 μm fraction suggest that the supply of clastic sediments is the main control on the magnetic properties of loess deposits in Central Asia. [ABSTRACT FROM AUTHOR]

In this paper, the crystallographic, magnetic, thermomagnetic, and magnetocaloric properties of the quenched NiMn1−xCrxGe (x = 0.04, 0.18, and 0.25) half-Heusler alloys have been studied by x-ray diffraction, differential scanning calorimetry and magnetization measurements. An influence of partial substitution of Cr for Mn and quenching of the samples on the character of structural and magnetic phase transitions is presented. Quenching of the alloys results in the formation of two phase (orthorhombic and hexagonal) crystal structure. The magnetic properties were investigated by means of magnetization measurements over a wide temperature (5–400 K) and magnetic field (up to 60 kOe) ranges. The experimental data indicate that at quenching and with increasing Cr content the magnetic order changes from antiferromagnetic to ferromagnetic. Hardened compounds exhibit a thermal hysteresis in the vicinity of the magnetic phase transition, what is characteristic for a first-order magnetic phase transition. The magnetic phase transition temperatures are decreased as a result of quenching of the samples. The magnetic entropy changes were calculated using the field dependences of isothermal magnetization in terms of the thermodynamic Maxwell relation. The magnetic entropy changes, |ΔSMmax|, obtained for the hardened alloys with x = 0.25 have the maximum value equal to 23 J/(kg·K) near the magnetic phase transition for a field change of ΔH = 0–60 kOe. [ABSTRACT FROM AUTHOR]

The main goal of this paper is to focus on the investigation of interaction between a magnetic field and elastic materials with microstructure, whose microelements possess microtemperatures with photothermal excitation. The elastic-photothermal problem in one-dimension is solved by introducing photothermal excitation at the free surface of a semi-infinite semiconducting medium (semiconductor rod). The integral transform technique is used to solve the governing equations of the problem under the effect of the microtemperature field. The analytical expressions for some physical quantities in the physical domain are obtained with the heating boundary surface and free traction. The numerical inversion technique is used to obtain the resulting quantities in the physical domain. The obtained numerical results with some comparisons are discussed and shown graphically. [ABSTRACT FROM AUTHOR]

Stability of the vortex matter—magnetic flux lines penetrating into the material—in type-II superconductor films is crucially important for their application. If some vortices get detached from pinning centres, the energy dissipated by their motion will facilitate further depinning, and may trigger an electromagnetic breakdown. In this paper, we review recent theoretical and experimental results on development of the above mentioned thermomagnetic instability. Starting from linear stability analysis for the initial critical-state flux distribution we then discuss a numerical procedure allowing to analyze developed flux avalanches. As an example of this approach we consider ultra-fast dendritic flux avalanches in thin superconducting disks. At the initial stage the flux front corresponding to the dendrite's trunk moves with velocity up to 100 km/s. At later stage the almost constant velocity leads to a specific propagation regime similar to ray optics. We discuss this regime observed in superconducting films coated by normal strips. Finally, we discuss dramatic enhancement of the anisotropy of the flux patterns due to specific dynamics. In this way we demonstrate that the combination of the linear stability analysis with the numerical approach provides an efficient framework for understanding the ultra-fast coupled nonlocal dynamics of electromagnetic fields and dissipation in superconductor films. [ABSTRACT FROM AUTHOR]

The thermomagnetic behavior of the as-quenched Cu-9wt%Al-10 wt%Mn-3wt%Gd alloy was studied using differential scanning calorimetry (DSC), optical microscopy, magnetization measurements with temperature and applied field. The results obtained showed that in the Cu-9wt%Al alloy the α, γ 1 and α 2 phases are produced from martensitic β′ phase decomposition while in the Cu-9wt%Al-3wt%Gd alloy the higher fraction of produced γ 1 phase is not formed from martensite decomposition. In the Cu-9wt%Al-10 wt%Mn and Cu-9wt%Al-10 wt%Mn-3wt%Gd alloys the ferromagnetic Cu 2 AlMn phase formation is dependent on the cooling rate and the martensitic transition seems to be changed by the presence of Gd. [ABSTRACT FROM AUTHOR]

Recent calculations of properties of TbAl 2 GdAl 2 and SmAl 2 single crystals, performed with our new computation system called ATOMIC MATTERS MFA are presented. We applied localized electron approach to describe the thermal evolution of Fine Electronic Structure of Tb 3+ , Gd 3+ and Sm 3+ ions over a wide temperature range and estimate Magnetocaloric Effect (MCE). Thermomagnetic properties of TbAl 2 , GdAl 2 and SmAl 2 were calculated based on the fine electronic structure of the 4 f 8 , 4 f 7 and 4 f 5 electronic configuration of the Tb 3+ and Gd 3+ and Sm 3+ ions, respectively. Our calculations yielded: magnetic moment value and direction; single-crystalline magnetization curves in zero field and in external magnetic field applied in various directions m (T, B ext ); the 4 f -electronic components of specific heat c 4f (T, B ext ); and temperature dependence of the magnetic entropy and isothermal entropy change with external magnetic field – ΔS(T, B ext ). The cubic universal CEF parameters values used for all CEF calculations was taken from literature and recalculated for universal cubic parameters set for the RAl 2 series: A 4  = +7.164 Ka 0 4 and A 6  = −1.038 Ka 0 6 . Magnetic properties were found to be anisotropic due to cubic Laves phase C15 crystal structure symmetry. These studies reveal the importance of multipolar charge interactions when describing thermomagnetic properties of real 4 f electronic systems and the effectiveness of an applied self-consistent molecular field in calculations for magnetic phase transition simulation. [ABSTRACT FROM AUTHOR]