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Exploiting two-dimensional van der Waals (2D vdW) room temperature ferromagnetic materials is always significant and valuable work. However, the actual number of satisfactory materials with intrinsic ferromagnetism is very limited. Here, the 2D layered Cr4Te5 epitaxial films prepared by a pulsed laser deposition technique were confirmed to hold a ferromagnetic ordering state up to 300 K. We find that the Cr4Te5 films can easily achieve epitaxial growth along a single orientation of the hexagonal Al2O3(0001) substrate. However, as for the cubic SrTiO3(001) and multiphase structure mica substrates, the Cr4Te5 films only show uniaxial growth instead of epitaxial growth. Based on the investigation of electronic transport in the metallic regime, it is revealed that the interaction of electron–magnon scattering only exists in the lower temperature region. Our work renders 2D vdW Cr4Te5 crystals a very promising material for developing practical spintronic nanodevices. [ABSTRACT FROM AUTHOR]

Apart from the impact of different substrates on epitaxial thin films due to lattice constant mismatches, the properties of epitaxial thin films are also influenced by the same substrates with different crystal orientations. Herein, the (111)‐oriented SrTiO3 (STO) substrates are used to fabricate the LaCoO3 (LCO) epitaxial thin films rather than the more common (001)‐oriented STO substrates. It undergoes one paramagnetic–ferromagnetic phase transition around 50 K. This phase transition is similar to the previously observed for (001)‐LCO/STO, but the Curie temperature (Tc) is significantly lower than the previously reported 80 K. To investigate the decrease of Tc and gain further insight into the phase transition, the critical behavior analysis of thin film is performed. The critical exponents are determined to be β = 1.591(3) and γ = 0.937(1) by reconstructing a modified Arrott plot, and the reliability of these exponents is confirmed by the Widom scaling relation. Using the renormalization group theory approach, it is discovered that the film has a long‐range magnetic interaction with space dimensionality d = 2 and spin dimensionality n = 1, and the magnetic exchange interaction decays J(r)≈r−2.4473. [ABSTRACT FROM AUTHOR]

We have presented the structural, surface morphology, magnetic and resistivity data for perovskite LaMnO3 epitaxial thin films which are fabricated on well-oriented (001) LaAlO3 substrates by pulsed laser deposition technique. X-ray diffraction 𝜃 – 2 𝜃 linear scans and reciprocal space mapping measurement confirm that the out-of-plane and in-plane epitaxial relationship are LMO(001)/LAO(001) and LMO(110)/LAO(110), respectively. Surface roughness determined by atomic force microscopy was no more than 0.3 nm. In the whole studied temperature range, all films only show a paramagnetic behavior instead of any magnetic phase transitions. Correspondingly, the electron transport behaviors always exhibit an insulting state as the temperature changes from high to low. However, we find that none of theoretical models can individually be used to understand their conductive mechanisms. Further studies indicated that charge carries of high and low temperature region obey adiabatic and nonadiabatic small polaronic hopping mechanisms, respectively. This finding offers new ways of exploiting the abnormal ferromagnetism in LaMnO3 multilayer thin films. [ABSTRACT FROM AUTHOR]

The critical behavior of single phase Y2Fe17 melt-spun ribbons with the Th2Fe17-type crystal structure has been studied around the transition temperature (TC). This alloy undergoes a second-order ferromagnetic (FM)–paramagnetic (PM) phase transition at TC = 301 K. Various techniques, such as the modified Arrott plot, Kouvel–Fisher method, and critical isotherm analysis, were used to determine the critical exponents that were found to be β = 0.226(3), γ = 1.296(2), and δ = 6.804(5). The universality class of the critical phenomenon in the Y2Fe17 ribbons can be explained with the help of the renormalization group theory approach, in which the magnetic properties show a feature changing from three (3D)- to two-dimensional (2D) Ising model. The first-principles calculations based on density functional theory qualitatively explain the experimental results, confirming the strong correlation between lattice atoms and critical behavior in magnetic intermetallic Y2Fe17. [ABSTRACT FROM AUTHOR]

High-quality epitaxial LaCoO3 (LCO) thin films have been deposited on SrTiO3 (STO) substrates with pulsed laser deposition (PLD). We find that the LCO films undergo a typical ferromagnetic–paramagnetic (FM–PM) phase transition at ∼80 K. To understand the nature of magnetic phase transition, various methods, including the modified Arrott plot and critical isotherm analysis, were used to determine the critical exponents, which are β = 0.754(1) with a Curie temperature TC = 79.8(8) K and γ = 1.52(2) with TC = 79.9(2) K. The reliability of these critical exponents was confirmed using the Widom scaling relation and the scaling hypothesis. Further analysis revealed that the spin coupling within the LCO films exhibits two-dimensional (2D) long-range magnetic interaction and the magnetic exchange distance decays as J(r) ∼ r−(3.46). Our critical behavior analysis may shed new light on the further understanding of the origin of FM and the relatively fixed TC in LCO thin films. [ABSTRACT FROM AUTHOR]

We have studied the magnetic coupling property, magnetic entropy change, and magnetic phase transition behavior of ternary alloy Ce 1. 3 Pr 0. 7 Co 7 . It exhibits a typical paramagnetic–ferromagnetic phase transition at T C = 2 1 8  K and this phase transition is verified to be second order by the scaling theory. Based on the data of isothermal magnetization measured around T C , we obtained the variation of its magnetic entropy change under the different magnetic fields but it only shows a smaller entropy change value. Density functional calculations confirm that the extra magnetic interaction originates from the Pr-Pr exchange interactions, which yields anomalous magnetic coupling with Co-Co (Ce-Ce) exchange interactions. One phenomenological model is suggested to understand anomalous magnetic behavior observed in the present intermetallic compounds. [ABSTRACT FROM AUTHOR]

In the present work, we have demonstrated that the coupling and decoupling between the magnetic and structural transitions can be manipulated by the partial replacement of the Mn by Zr in the MnCoGe alloys. Energy-dispersive spectroscopy analyses reveal a homogeneous distribution of the Zr atoms throughout the samples. The differential scanning calorimetry and X-ray diffraction results reveal a decrease in the structural transition temperature Tt with an increase in the Zr content. A strong magneto-structural coupling can be realized in the Mn1−xZrx CoGe with 0.04 ≤ x ≤ 0.07, where the Tt is lowered to the temperature range between the Curie temperatures of the orthorhombic and hexagonal phases. The magneto-structural transition is accompanied with significant changes in the interatomic distances between the magnetic atoms, which strongly influence both the magnetic exchange interactions and the chemical bonding. As a result, a coincidence of the magnetic and structural transitions is observed, which brings a giant magnetocaloric effect due to the contributions from both the lattice and the magnetic entropy changes. [ABSTRACT FROM AUTHOR]

The temperature-dependent spin-reorientation transition (SRT) and spin interaction mechanism of bulk TmFeO3 were studied by the electron paramagnetic resonance (EPR) method. The combined experimental results of magnetic curves and EPR spectra confirmed that there is an antiferromagnetic transition at 85 K with a reentering ferromagnetic state due to the spin-reorientation behavior. In the high-temperature region of T > 90 K, there are three distinct resonance peaks in the EPR spectrum, which indicates the presence of multiple magnetic phases (canted antiferromagnetic, weak ferromagnetic, and paramagnetic phases). In the low-temperature region (T < 85 K), the temperature dependence of the EPR linewidth, effective g-factor, and intensity can be used to infer a strong spin–lattice correlation. Different magnetic interactions such as Fe3+–Fe3+, Fe3+–Tm3+, and Tm3+–Tm3+ lead to a paramagnetic–canted antiferromagnetic phase at T > 85 K, with SRT between 85–65 K and ferromagnetic interaction at the lower temperature, respectively. Above 90 K, we find that the spin relaxation mechanism is determined by the mixture of spin–spin and spin–lattice interactions. Below 85 K, the transverse relaxation rate increases with the decrease in temperature, which is consistent with the weakening of the fluctuating internal field in this temperature region. This EPR detection provides a new method to clarify the strong spin coupling in antiferromagnetic materials. [ABSTRACT FROM AUTHOR]

Due to environmental concerns and the increasing drive towards miniaturization of electronic circuits and devices, lead-free ferroelectric films with low leakage current and robust ferroelectric and piezoelectric properties are highly desired. The preferred alternative, BaTiO3, is non-toxic and has ferroelectric properties, but its high leakage current, poor ferroelectricity and piezoelectricity and low Curie temperature of ∼130 °C in thin film form are obstacles for high-temperature practical applications. Here, we report that a negative-pressure-driven enhancement of ferroelectric Curie temperature and effective piezoelectric coefficient are achieved in (111)-oriented BaTiO3 nanocomposite films. The enhanced ferroelectric and piezoelectric properties in the emergent monoclinic BaTiO3 are attributed to the sharp vertical interface and 3D tensile strain that develops upon interspersing stiff and self-assembled vertical Sm2O3 nanopillars through the film thickness. Our work also demonstrates that fabricating oxide films through (111)-oriented epitaxy opens up new avenues for the creation of new phase components and exploration of novel functionalities for developing oxide quantum electronic devices. [ABSTRACT FROM AUTHOR]

The magnetic and electronic transport properties of the lightly doped SrRu1-x Fex O3 (x ≤ 0.15) have been studied. All the samples show a paramagnetic-ferromagnetic phase transition and hysteresis effect. With the increase of Fe, the temperature of magnetic phase transition decreases but coercive field increases indicting the existence of antiferromagnetic interaction and magnetic-crystalline anisotropy. In low temperature, all the doping samples exhibit an insulating behavior while metal feature appears only at x ≤ 0.10 samples. The induced disorder suppresses the itinerant property of Ru 4d electron due to Fe random occupation. As a result, the ferromagnetism is weakened and metal-insulator transition is suppressed. [ABSTRACT FROM AUTHOR]

We report a detailed study of magnetic and transport properties in perovskite manganites Nd0.55Sr0.45Mn1-xGaxO3 (0.00≤x≤0.20). The Ga substitution induces the B-site disorder together with a distinct suppression of the metal-insulator transition and ferromagnetic-paramagnetic transition. Due to an appearance of inhomogeneous magnetic clusters, the Griffiths-like phase is observed in 0.08≤x≤0.10 compounds. Meanwhile, with the increase of Ga concentration, the carriers self-trap into magnetic polarons. Because the oxygen sublattice distortion causes the variation of the phonon density of state, an additional Raman vibrative mode appears in the system. [ABSTRACT FROM AUTHOR]

The electronic transport and magnetism in half-doped Nd0.50Ca0.25Sr0.25MnO3 manganites have been investigated. Contrary to general half-doped system, it only displays a paramagnetic-ferromagnetic phase transition associated with an insulator-metal transition instead of with any features of charge ordering. With the decrease of temperature, an electronic phase separation and spin glass state occur in low temperature. We suggest that the A-site cation disorder induced by the size mismatch between Sr2+ ion and Ca2+ ion is mainly responsible for this phenomenon. [ABSTRACT FROM AUTHOR]

In this paper, we study the absorption efficiency spectra of Au nanoparticles enveloped with Fe3O4 nanoshell by applying the discrete dipole approximation method. Three kinds of Au@Fe3O4 core-shell nanohybrids (NHs) structure, including the same core with different shell thickness, the same outer shell with different core radius, and the same size of total radius, have been discussed in detail. The simulation results show that the square of localized surface plasmon resonance (LSPR) peak wavelength of NHs is linearly proportional with the volume fraction of the shell, regardless of the outer shell material properties. Compared to the plasmon resonance peak of the Au nanoparticles, the LSPR shift of the NHs is dependent on both the total particles size and the outer Fe3O4 shell thickness. Our calculation results would provide some key guidances to design the structure variables of NHs for a broad range of plasmon applications. [ABSTRACT FROM AUTHOR]

We report the physical properties of Eu-doped bulk TmFeO3 through X-ray diffraction, magnetic susceptibility (χ), Raman scattering and X-ray absorption spectroscopy (XAS) study, which shows a similar orthorhombic structure with the Pbnm space group as TmFeO3. Magnetic measurement on Eu-doped TmFeO3 provides evidence for spin reorientations of Fe3+. Further, the Raman spectra of Eu3+ doped TmFeO3 show significant changes in Raman modes as a function of temperature, which are evidence for strong spin–lattice interaction. From the XAS spectra, the L-edge of Fe provides information on the valence state of Fe, whereas the K-edge of oxygen shows that the compound has a strong influence on the hybridization of the O(2p) state with the 3d states of Fe. [ABSTRACT FROM AUTHOR]

• The electronic phase separation has been observed in La 0.8 Sr 0.2 MnO 3. • The state of magnetic skyrmion exists in the temperature region of 290 K–306 K. • A large DM interaction exists in the interface of LaMnO 3 /SrMnO 3. Magnetic skyrmions, being one of the most promising candidates for the next generation memory-type application due to their nanometer-size and efficient current-driven dynamics, are mainly found and studied in alloy helimagnets in which the spin-orbit coupling induced by Dzyaloshinskii-Moriya interaction (DMI) enables noncollinear spin alignment and skyrmion formation. In this paper, we report a possible finding of skyrmions crystal near room-temperature in centrosymmetric structures perovskite manganite La 0.8 Sr 0.2 MnO 3 (LSMO). Based on the measurements of isothermal magnetization around the Curie temperature (∼298 K), an unusual magnetic behavior of a discontinuous magnetization was observed and existed only at moderate magnetic field region together with a narrow temperature range from 306 to 290 K. Apart from this range, all curves return to conventional magnetic behavior of continuous change with external magnetic field. This characteristic has been frequently observed in some reported helimagnets (such as FeGe, MnSi), implying the possible existence of skyrmions crystal in LSMO. To further unveil the physical origin and underlying mechanisms, we performed the first-principles calculation for LSMO compound and a large DMI (Δ E DMI = 13.46 meV, d 1 = 1.68 meV) was found to exists at the interface of LaMnO 3 / SrMnO 3 layers. This result not only supports our experimental findings in the present composition but also is consistent with the formation mechanism of magnetic skyrmions. [ABSTRACT FROM AUTHOR]

The structural, Hall effect, electronic transport, and magnetic properties of Ge0.96−xBixFe0.04Te epitaxial thin film as prepared by pulsed laser deposition technique were reported. X-ray diffraction patterns including linear scans and phi scans confirmed that all films are high quality epitaxy and crystallinity. With the substitution of high valence Bi for Ge element, we found that the previous carriers of hole were changed to electron, which was testified by the negative slopes obtained from the measurements of Hall effect under different temperatures. The electronic transports show a typical semiconductor behavior and can be understood by the small polaron hopping model because the lattice distortions increase the electron-phonon interaction. An obvious ferromagnetic properties occur in the high Bi-doping Ge0.64Bi0.32Fe0.04Te rather than in that with low Bi-doping concentration, indicating that the ferromagnetic establishment is entirely dependent on carrier's transmissions. The first-principles calculation performed on this system also reveals that the ferromagnetic state exactly exists in the present n-type diluted magnetic semiconductors with Bi co-dopants. [ABSTRACT FROM AUTHOR]