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Below a critical temperature [Formula: see text], superconductors transport electrical charge without dissipative energy losses. The application of a magnetic field [Formula: see text] generally acts to suppress [Formula: see text], up to some critical field strength at which [Formula: see text] 0 K. Here, we investigate magnetic field-induced superconductivity in high-quality specimens of the triplet superconductor candidate UTe[Formula: see text] in pulsed magnetic fields up to [Formula: see text] [Formula: see text] 70 T. Strikingly, we find that this material has a higher [Formula: see text] when [Formula: see text] 40 T ([Formula: see text] 2.4 K) than it does for [Formula: see text] 0 T ([Formula: see text] 2.1 K). This observation points to a fundamentally distinct mechanism for the formation of superconductivity at high [Formula: see text] in UTe[Formula: see text] compared to the case of [Formula: see text] [Formula: see text] 0 T., Competing Interests: Competing interests statement:The authors declare no competing interest.

The unconventional superconductor UTe[Formula: see text] exhibits numerous signatures of spin-triplet superconductivity-a rare state of matter which could enable quantum computation protected against decoherence. UTe[Formula: see text] possesses a complex phase landscape comprising two magnetic field-induced superconducting phases, a metamagnetic transition to a field-polarized state, along with pair- and charge-density wave orders. However, contradictory reports between studies performed on UTe[Formula: see text] specimens of varying quality have severely impeded theoretical efforts to understand the microscopic origins of the exotic superconductivity. Here, we report a comprehensive suite of high magnetic field measurements on a generation of pristine quality UTe[Formula: see text] crystals. Our experiments reveal a significantly revised high magnetic field superconducting phase diagram in the ultraclean limit, showing a pronounced sensitivity of field-induced superconductivity to the presence of crystalline disorder. We employ a Ginzburg-Landau model that excellently captures this acute dependence on sample quality. Our results suggest that in close proximity to a field-induced metamagnetic transition the enhanced role of magnetic fluctuations-that are strongly suppressed by disorder-is likely responsible for tuning UTe[Formula: see text] between two distinct spin-triplet superconducting phases., Competing Interests: Competing interests statement:The authors declare no competing interest.

UTe_{2} is a spin-triplet superconductor candidate for which high quality samples with long mean free paths have recently become available, enabling quantum oscillation measurements to probe its Fermi surface and effective carrier masses. It has recently been reported that UTe_{2} possesses a 3D Fermi surface component [Phys. Rev. Lett. 131, 036501 (2023)PRLTAO0031-900710.1103/PhysRevLett.131.036501]. The distinction between 2D and 3D Fermi surface sections in triplet superconductors can have important implications regarding the topological properties of the superconductivity. Here we report the observation of oscillatory components in the magnetoconductance of UTe_{2} at high magnetic fields. We find that these oscillations are well described by quantum interference between quasiparticles traversing semiclassical trajectories spanning magnetic breakdown networks. Our observations are consistent with a quasi-2D model of this material's Fermi surface based on prior dHvA-effect measurements. Our results strongly indicate that UTe_{2}-which exhibits a multitude of complex physical phenomena-possesses a remarkably simple Fermi surface consisting exclusively of two quasi-2D cylindrical sections.

CrI 3 represents one of the most important van der Waals systems on the route to understanding 2D magnetic phenomena. Being arranged in a specific layered structure, it also provides a unique opportunity to investigate structural transformations in dimension-confined systems. CrI 3 is dimorphic and possesses a higher symmetry low-temperature phase, which is quite uncommon. It contrasts with vanadium trihalides, which show a higher symmetry high-temperature phase. An explanation of this distinct behavior, together with a large cycle-dependent transition hysteresis, is still an open question. Our low-temperature X-ray diffraction study conducted on CrI 3 single crystals complemented by magnetization and specific heat measurements was focused mainly on specific features of the structural transition during cooling. Our results manifest that the structural transition during cooling relates to the formation of structural domains despite the lower symmetry structure transforming to a higher symmetry one. We propose that these domains could control the size of thermal hysteresis.

The heavy fermion paramagnet UTe 2 exhibits numerous characteristics of spin-triplet superconductivity. Efforts to understand the microscopic details of this exotic superconductivity have been impeded by uncertainty regarding the underlying electronic structure. Here we directly probe the Fermi surface of UTe 2 by measuring magnetic quantum oscillations in pristine quality crystals. We find an angular profile of quantum oscillatory frequency and amplitude that is characteristic of a quasi-2D Fermi surface, which we find is well described by two cylindrical Fermi sheets of electron- and hole-type respectively. Additionally, we find that both cylindrical Fermi sheets possess considerable undulation but negligible small-scale corrugation, which may allow for their near-nesting and therefore promote magnetic fluctuations that enhance the triplet pairing mechanism. Importantly, we find no evidence for the presence of any 3D Fermi surface sections. Our results place strong constraints on the possible symmetry of the superconducting order parameter in UTe 2 ., (© 2024. The Author(s).)

The existence of the V 3+ -ion orbital moment is an open issue of the nature of magnetism in the van der Waals ferromagnet VI 3 . The huge magnetocrystalline anisotropy in conjunction with the significantly reduced ordered magnetic moment compared to the spin-only value provides strong but indirect evidence of a large V orbital moment. We used the unique capability of X-ray magnetic circular dichroism to determine the orbital component of the total magnetic moment and provide a direct proof of an exceptionally sizable orbital moment of the V 3+ ion in VI 3 . Our ligand field multiplet simulations of the XMCD spectra in synergy with the results of DFT calculations agree with the existence of two V sites with different orbital occupations and OM magnitudes in the ground state.

We use the synergy of infrared, terahertz, and Raman spectroscopies with DFT calculations to shed light on the magnetic and lattice properties of VI 3 . The structural transition at T S1 = 79 K is accompanied by a large splitting of polar phonon modes. Below T S1 , strong ferromagnetic fluctuations are observed. The variations of phonon frequencies at 55 K induced by magnetoelastic coupling enhanced by spin-orbit interaction indicate the proximity of long-range ferromagnetic order. Below T C = 50 K, two Raman modes simultaneously appear and show dramatic softening in the narrow interval around the temperature T S2 of the second structural transition associated with the order-order magnetic phase transition. Below T S2 , a magnon in the THz range appears in Raman spectra. The THz magnon observed in VI 3 indicates the application potential of 2D van der Waals ferromagnets in ultrafast THz spintronics, which has previously been considered the exclusive domain of antiferromagnets.

Most transition-metal trihalides are dimorphic. The representative chromium-based triad, CrCl 3 , CrBr 3 , CrI 3 , is characterized by the low-temperature (LT) phase adopting the trigonal BiI 3 -type while the structure of the high-temperature (HT) phase is monoclinic of AlCl 3 type ( C 2/ m ). The structural transition between the two crystallographic phases is of the first-order type with large thermal hysteresis in CrCl 3 and CrI 3 . We studied crystal structures and structural phase transitions of vanadium-based counterparts VCl 3 , VBr 3 , and VI 3 by measuring specific heat, magnetization, and x-ray diffraction as functions of temperature and observed an inverse situation. In these cases, the HT phase has a higher symmetry while the LT structure reveals a lower symmetry. The structural phase transition between them shows no measurable hysteresis in contrast to CrX 3 . Possible relations of the evolution of the ratio c / a of the unit cell parameters, types of crystal structures, and nature of the structural transitions in V and Cr trihalides are discussed., (© 2022 IOP Publishing Ltd.)

We present acoustic signatures of the electric quadrupolar degrees of freedom in the honeycomb-layer compound UNi_{4}B. The transverse ultrasonic mode C_{66} shows softening below 30 K both in the paramagnetic phase and antiferromagnetic phases down to ∼0.33  K. Furthermore, we traced magnetic field-temperature phase diagrams up to 30 T and observed a highly anisotropic elastic response within the honeycomb layer. These observations strongly suggest that Γ_{6}(E_{2g}) electric quadrupolar degrees of freedom in localized 5f^{2} (J=4) states are playing an important role in the magnetic toroidal dipole order and magnetic-field-induced phases of UNi_{4}B, and evidence some of the U ions remain in the paramagnetic state even if the system undergoes magnetic toroidal ordering.

Magnetotransport constitutes a useful probe to understand the interplay between electronic band topology and magnetism in spintronic devices. A recent theory of Lu and Shen [Phys. Rev. Lett. 112, 146601 (2014)PRLTAO0031-900710.1103/PhysRevLett.112.146601] on magnetically doped topological insulators predicts that quantum corrections Δκ to the temperature dependence of conductivity can change sign across the Curie transition. This phenomenon has been attributed to a suppression of the Berry phase of the topological surface states at the Fermi level, caused by a magnetic energy gap. Here, we demonstrate experimentally that Δκ can reverse its sign even when the Berry phase at the Fermi level remains unchanged. The contradictory behavior to theory predictions is resolved by extending the model by Lu and Shen to a nonmonotonic temperature scaling of the inelastic scattering length showing a turning point at the Curie transition.

YFeO 3 and LaFeO 3 are members of the rare-earth orthoferrites family with Pbnm space group. Using inelastic neutron scattering, the low-energy spin excitations have been measured around the magnetic Brillouin zone center. Splitting of magnon branches and finite magnon gaps (∼2 meV) are observed for both compounds, where the Dzyaloshinsky-Moriya interactions account for most of this gap with some additional contribution from single-ion anisotropy. We also make comparisons with multiferroic BiFeO 3 (R3c space group), in which similar behavior was observed. By taking into account all relevant local Dzyaloshinsky-Moriya interactions, our analysis allows for the precise determination of all experimentally observed parameters in the spin-Hamiltonian. We find that different properties of the Pbnm and R3c space group lead to the stabilization of a spin cycloid structure in the latter case but not in the former, which explains the difference in the levels of complexity of magnon band structures for the respective compounds.

Many current research efforts in strongly correlated systems focus on the interplay between magnetism and superconductivity. Here we report on coexistence of both cooperative ordered states in recently discovered stoichiometric and fully inversion symmetric heavy fermion compound Ce3PdIn11 at ambient pressure. Thermodynamic and transport measurements reveal two successive magnetic transitions at T1 = 1.67 K and TN = 1.53 K into antiferromagnetic type of ordered states. Below Tc = 0.42 K the compound enters a superconducting state. The large initial slope of dBc2/dT ≈ - 8.6 T/K indicates that heavy quasiparticles form the Cooper pairs. The origin of the two magnetic transitions and the coexistence of magnetism and superconductivity is briefly discussed in the context of the coexistence of the two inequivalent Ce-sublattices in the unit cell of Ce3PdIn11 with different Kondo couplings to the conduction electrons.

The transformation of Mn(II) glycolates (glc) between the three-dimensional coordination polymer [Mn(glc)2]n (1) and discrete mononuclear phase [Mn(glc)2 (H2O)2] (2) can be reversibly switched by water molecules, which dramatically change the magnetocaloric effect (MCE) of Mn(II) glycolates from the maximum of 6.9 J kg(-1)  K(-1) in 1 to 60.3 J kg(-1)  K(-1) in 2. This case example reveals that the effect of magnetic coupling on MCE plays a dominant role over that of other factors such as magnetic density for 3d-type magnetic refrigerants., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The comprehensive study reported herein provides compelling evidence that anion templates are the main driving force in the formation of two novel nanoscale lanthanide hydroxide clusters, {Gd38(ClO4)6} (1) and {Gd48Cl2(NO3)} (2), characterized by single-crystal X-ray crystallography, infrared spectroscopy, and magnetic measurements. {Gd38(ClO4)6}, encapsulating six ClO4(-) ions, features a cage core composed of twelve vertex-sharing {Gd4} tetrahedrons and one Gd⋅⋅⋅Gd pillar. When Cl(-) and NO3(-) were incorporated in the reaction instead of ClO4(-), {Gd48Cl2(NO3)} is obtained with a barrel shape constituted by twelve vertex-sharing {Gd4} tetrahedrons and six {Gd5} pyramids. What is more, the cage-like {Gd38} can be dynamically converted into the barrel-shaped {Gd48} upon Cl(-) and NO3(-) stimulus. To our knowledge, it is the first time that the linear M-O-M' fashion and the unique μ8-ClO4(-) mode have been crystallized in pure lanthanide complex, and complex 2 represents the largest gadolinium cluster. Both of the complexes display large magnetocaloric effect in units of J kg(-1) K(-1) and mJ cm(-3) K(-1) on account of the weak antiferromagnetic exchange, the high N(Gd)/M(W) ratio (magnetic density), and the relatively compact crystal lattice (mass density)., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We report on detailed low-temperature measurements of the magnetization, the specific heat and the electrical resistivity on high-quality CeRuSn single crystals. The compound orders antiferromagnetically at T(N) = 2.8 K with the Ce(3+) ions locked within the a-c plane of the monoclinic structure. Magnetization shows that below T(N) CeRuSn undergoes a metamagnetic transition when applying a magnetic field of 1.5 and 0.8 T along the a- and c-axis, respectively. This transition manifests in a tremendous negative jump of ~25% in the magnetoresistance. The value of the saturated magnetization along the easy magnetization direction (c-axis) and the magnetic entropy above T(N) derived from specific heat data correspond to the scenario of only one third of the Ce ions in the compound being trivalent and carrying a stable Ce(3+) magnetic moment, whereas the other two thirds of the Ce ions are in a nonmagnetic tetravalent and/or mixed valence state. This is consistent with the low-temperature CeRuSn crystal structure i.e., a superstructure consisting of three unit cells of the CeCoAl type piled up along the c-axis, and in which the Ce(3+) ions are characterized by large distances from the Ru ligands while the Ce-Ru distances of the other Ce ions are much shorter causing a strong 4f-ligand hybridization and hence leading to tetravalent and/or mixed valence Ce ions.

Two kinds of inorganic gadolinium(III)-hydroxy "ladders", [2×n] and [3×n], were successfully trapped in succinate (suc) coordination polymers, [Gd2(OH)2(suc)2(H2O)]n·2nH2O (1) and [Gd6(OH)8(suc)5(H2O)2 ]n·4n H2O (2), respectively. Such coordination polymers could be regarded as alternating inorganic-organic hybrid materials with relatively high density. Magnetic and heat capacity studies reveal a large cryogenic magnetocaloric effect (MCE) in both compounds, namely (ΔH=70 kG) 42.8 J kg(-1) K(-1) for complex 1 and 48.0 J kg(-1) K(-1) for complex 2. The effect of the high density is evident, which gives very large volumetric MCEs up to 120 and 144 mJ cm(-3) K(-1) for complexes 1 and 2, respectively., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We report on a comprehensive investigation of the magnetic properties of [NdCo(bpdo)(H2O)4(CN)6]⋅3H2O (bpdo=4, 4'-bipyridine-N,N'-dioxide) by use of electron paramagnetic resonance, magnetization, specific heat and susceptibility measurements. The studied material was identified as a magnet with an effective spin S = 1/2 and a weak exchange interaction J/kB = 25 mK. The ac susceptibility studies conducted at audio frequencies and at temperatures from 1.8 to 9 K revealed that the application of a static magnetic field induces a slow spin relaxation. It is suggested that the relaxation in the magnetic field appears due to an Orbach-like process between the two lowest doublet energy states of the magnetic Nd(3+) ion. The appearance of the slow relaxation in a magnetic field cannot be associated with a resonant phonon trapping. The obtained results suggest that the relaxation is influenced by nuclear spin driven quantum tunnelling which is suppressed by external magnetic field.

We report on the specific heat, magnetization and ac susceptibility measurements of single crystals of hybrid frustrated magnets Gd(1.8)Tb(0.2)Ti(2)O(7) and Gd(1.5)Tb(0.5)Ti(2)O(7). The analysis of experimental data revealed that, although partial replacing of the Gd(3+) ions by the Tb(3+) ions in the Gd(2)Ti(2)O(7) host lattice slightly enhances antiferromagnetic coupling, as inferred from the evolution of the paramagnetic Curie-Weiss temperature, the ordering temperature gradually decreases. Paramagnetic correlations introduced by the Tb(3+) ions cause this perturbation, altering the effective further neighbor interactions and destabilizing the ground state in Gd(2)Ti(2)O(7). In addition, the low-energy states of Gd(2-x)Tb(x)Ti(2)O(7) are suggested to possess a nature different from those in parent members Tb(2)Ti(2)O(7) and Gd(2)Ti(2)O(7). Finally, the frequency-dependent magnetic susceptibility behavior in Gd(1.5)Tb(0.5)Ti(2)O(7) is consistent with the formation of a spin-glass-like state indicating a pronounced slowing down of the dynamical response of the studied hybrid magnets., (© 2012 IOP Publishing Ltd)

UNiGa crystallizes in the hexagonal ZrNiAl structure and orders antiferromagnetically below T(N)=39.3 K with the U moments oriented along the c-axis (easy magnetization axis). There are four different antiferromagnetic phases in zero magnetic field and two field induced magnetic phases in UNiGa. For all of them, a strong uniaxial anisotropy is encountered. All the magnetic phases are described by propagation vectors of (0 0 q(i))-type, where q(i) describes the stacking of the ferromagnetic basal planes along the hexagonal c-axis. However, recently (0 0 L)-type Bragg reflections associated with the magnetic ordering have been observed by neutron diffraction. Based on unpolarized and polarized neutron diffraction and non-resonant and resonant synchrotron x-ray scattering experiments combined with polarization analysis we conclude that small amounts of magnetic moments oriented perpendicular to the c-axis exist in UNiGa. Whether these moments reside on Ni atoms outside the U-Ni planes or at interstitial regions could not be determined., (© 2011 IOP Publishing Ltd)

For many years, micromagnetism and Monte Carlo simulation have served as the two main tools for studying the magnetic structures and physical properties of nanomagnets. However, the two approaches are based on classical physics, and thus lack the flexibility to deal with complex nanosystems, such as those of very tiny size or consisting of ions of different elements. To overcome the difficulty, a quantum simulation model has been proposed and a new computational algorithm developed in the present work. Both have been successfully applied to an assumed PrAl₂ nanoparticle to study its magnetic behavior in external magnetic fields exerted along the crystal axes. The theoretical results obtained with the model and the new algorithm are reasonable physically and exhibit strong finite-size effects. The model can be generalized to study the magnetic configurations and physical properties of more complicated nanosystems, such as nanowires, nanotubes, etc.