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The influence of biaxial strain on both the electronic and magnetic properties in double perovskite La2FeMnO6 is investigated by using density-functional calculations. The results show that La2FeMnO6 exhibits ferromagnetic semiconductor at ambient condition and turns into ferromagnetic half-metal under the whole tensile strain applied in this work, while the compound transfers into ferromagnetic metal under the compressive strain within -8% and into ferrimagnetic semiconductor with the compressive strain beyond -9%. For both ferromagnetic half-metallic and metallic La2FeMnO6, they exhibit very slight change in the electronic states and magnetic moments of the ions, comparing with those of the compound at ambient condition. The electronic configurations of Fe and Mn originating from the high-spin state Fe3+ and intermediate-spin state Mn3+ in ferromagnetic La2FeMnO6 emerge in the low-spin state and high-spin state in ferrimagnetic La2FeMnO6, respectively, when the compressive strain is beyond -9%. [ABSTRACT FROM AUTHOR]

Half-doped perovskite Manganese oxide has been widely studied because of its excellent properties such as colossal magnetoresistance (CMR) effect and charge-ordered (CO) phase separation. In this work, four Sm0.5Ca0.5MnO3 samples with different particle sizes are prepared by high-temperature solid-state reaction and ball milling. The crystal structure of the samples is studied by X-ray diffraction (XRD). The Sm0.5Ca0.5MnO3 sample is single phase, which belongs to orthorhombic structure. The surface morphology and particle size of the samples are examined by scanning electron microscope (SEM). The average particle size of the sample without ball milling is about 4 μm. With ball milling time for 12 h, 24 h, and 36 h, the particle size decreases, and finally it reaches hundreds to tens of nanometers. This shows that ball milling is an effective way to control the particle size. The M–T curves and M–H hysteresis loops of the samples are measured by physical properties measurements systems (PPMS). The two M–T curves measured in the warming and cooling processes do not overlap for Sm0.5Ca0.5MnO3 without ball milling, and the phenomenon of thermal hysteresis appears. Meanwhile, the M–T curve has a significant protuberance peak near 270 K. All of these indicate the CO behavior, whereas the particle size of Sm0.5Ca0.5MnO3 decreases with different milling times (12–36 h) and the CO phase is suppressed gradually, which leads to the decrease of CO temperature, magnetization, remanence, and coercivity. [ABSTRACT FROM AUTHOR]

The high-pressure effect on the physical properties in double perovskite Sr2FeMoO6 is explored theoretically. The structure of Sr2FeMoO6 exhibits I4/mmm symmetry in the whole external hydrostatic pressure applied. A spin crossover of Fe ion from high-spin to low-spin state is found at the pressure of about 33-36 GPa, accompanied by a transition from ferrimagnetic half-metallic to nonmagnetic semiconductor state. When the pressure is above 45 GPa, the nonmagnetic compound behaves as full metal. By the mean-field theory, the estimated Curie temperature of the ferrimagnetic Sr2FeMoO6 increases from 472 to 639 K when the pressure increases from 0 to 30 GPa. [ABSTRACT FROM AUTHOR]

Using density-functional calculations within the generalized gradient approximation plus U framework, the electronic and magnetic properties of the ordered and the disordered Sr2FeCoO6 are investigated systematically. The results show that all disordered Sr2FeCoO6 have ferromagnetic ground state, as that of the ordered one. The magnetic coupling of both Fe and Co sublattices remains ferromagnetic, and the two sublattices are coupled ferromagnetically as well. Most interestingly, the disorder leads to the substantial increase of the magnetic moments on both Fe and Co sites comparing with those of the ordered Sr2FeCoO6. It is also significantly found that the disorder can control the transport property, decreasing the half-metallic band gap of the ordered Sr2FeCoO6 and even giving rise to a half-metal to metal transition at a critical level of disorder. [ABSTRACT FROM AUTHOR]

In this work, we report the attractive magnetic properties of La1-xCaxMnO3 manganites with x = 0.2 (LCMO-2) and x = 0.5 (LCMO-5). X-ray diffraction (XRD) measurements show that the prepared samples are single phase and they crystallize in the orthorhombic structure with Pnma space group. Scanning electron microscope (SEM) measurements reveal that the particles of samples are homogeneous and possess the diameter of several microns. Magnetization versus temperature measurements show paramagnetic (PM) to ferromagnetic (FM) transition at TC ≈ 200 K for LCMO-2 and at TC ≈ 250 K for LCMO-5. Below TC, FM nature is observed in LCMO-2. However, LCMO-5 displays the complex magnetic phase transition. Below TC, LCMO-5 shows a FM to charge-ordered antiferromagnetic (COAFM) transition at CO temperature TCO and a novel, unexpected FM phase transition at characteristic temperature T* (near 35 K). The FM and COAFM phases coexist in LCMO-5, and the competition of FM and AFM phases lead to the unexpected FM transition at T*. Furthermore, the inverse of susceptibility versus temperature measurements confirm the similar results. Magnetic hysteresis loop measurements suggest the typical FM feature of LCMO-2. However, LCMO-5 exhibits the hysteresis loops with butterfly-type structure at 100 and 150 K, suggesting the presence of COAFM phase. These attractive magnetic properties are explained by the existence of COAFM phase and the competition between FM and COAFM phases. [ABSTRACT FROM AUTHOR]

The structural and magnetic properties of Y2−xSrxCoMnO6 (0 ≤ x ≤ 0.5) compounds are investigated in this report. X-ray photoelectron spectroscopy reveals that Co and Mn ions are presented in the form of Co2+/Co3+ and Mn3+/Mn4+, respectively. The broadening of Raman spectra suggests the existence of antisite disorders in these double perovskite oxides. The ferromagnetic transition temperature slightly increases with Sr doping, while the saturated magnetic moment shows a substantial decrease, further confirming the presence of Co/Mn antisite disorders. The signature of exchange bias effect in Y2−xSrxCoMnO6 (0 ≤ x ≤ 0.5) double perovskites has been observed, which is demonstrated by the displacement of field-cooled magnetic hysteresis loops. Moreover, the exchange bias field is strongly correlated with the degree of antisite disorders and reaches a maximum of 3.4 kOe for x = 0.25. The origin of exchange bias effect can be explained as the interfacial exchange coupling between ferromagnetic regions and antiferromagnetic antiphase boundaries created by antisite disorders in these specimens. [ABSTRACT FROM AUTHOR]

We have grown PrSrMnO/LaCaMnO bilayer on (001) single crystal SrTiO substrate by pulsed laser deposition technique. The bilayer film is well (001) orientation grown with high crystalline quality. When the applied magnetic field increases up to 9 T, only metal-like transport behavior can be observed below room temperature. The Low-field MR (LFMR) as large as ~−73% has been achieved at an applied field of 1 T and the magnetoresistance (MR) can reach a value of ~−641% at an applied field of 9 T. Ferromagnetic (FM) clusters percolation accompanied with the collapse (melting) of charge-ordered (CO) state in LaCaMnO may be responsible for the enhancement of MR. Moreover, the disappearance of exchange bias (EB) in the bilayer demonstrates the existence of FM clusters percolation at the PSMO/LCMO interface. Large LFMR provides possibilities in developing manganite-based FM/CO film devices. [ABSTRACT FROM AUTHOR]

The phase transitions of melt-spun Ni50Mn35In15 ribbons are modulated with post-annealing. Both the martensitic transformation temperatures and Curie temperature of the austenitic phase increase after post-annealings. However, the maxima of phase transition temperatures are obtained after 873 K annealing, instead of higher-temperature annealings. The nonmonotonic dependences exclude Mn volatilization and grain growth from the dominant reason. The superlattice reflections in Heusler structure indicate that the increases of phase transition temperatures should be related to the increment of L21 atomic order. [ABSTRACT FROM AUTHOR]

Abstract: The effects of surface modification on the topological surface states in Bi2Se3 have been studied using first-principles calculations. Although surface modification cannot change the topological order, however, the spin polarization, dispersion of topological surface bands and the position of Dirac points are altered. All the studied surface modifications can push Dirac cone upwards effectively. Bi-capped surface can attract the quantum well states into bulk band gap, forming new Dirac cone at point. Both Bi-capped and Se-removed surface can slightly enhance spin polarization of topological surface states, while flatten the energy dispersion of the topological surface bands above Dirac point. [Copyright &y& Elsevier]

The magnetic behaviors and magnetocaloric effect (MCE) of Pr 0.7 Sr 0.3 MnO 3 (PSMO-7) film grown on a (001) SrTiO 3 single-crystal substrate by a pulsed laser deposition (PLD) were studied in this paper. X-ray diffraction with a high resolution (HRXRD) measurement shows that PSMO-7 film is grown with a (001) single orientation. The magnetic properties and the MCE related to the ferromagnetic (FM) phase transition of the PSMO-7 film are investigated using the temperature dependence of magnetization M(T) and the magnetic field dependence of magnetization M(H). The M(T) data suggest that with decreasing temperatures, the PSMO-7 film goes through the transition from the paramagnetic (PM) state to the FM state at around the Curie temperature (T C ). The T C (about 193 K) can be obtained by the linear fit of the Curie law. Magnetic hysteresis loop measurements show that the PSMO-7 film exhibits the FM feature at temperatures of 10, 100, and 150 K (low magnetic hysteresis can be found), while the film reveals the PM feature with the temperature increased up to 200 and/or 300 K. The research results of M(H) data are consistent with the M(T) data. Furthermore, the magnetic entropy change (-ΔSM) of the PSMO-7 film was studied. It was found that the maximum value of (-ΔSM) near T C reaches about 4.7 J/kg·K under the applied field change of 20 kOe, which is comparable to that of metal Gd (-ΔSM of 2.8 J/kg K under 10 kOe), indicating the potential applications of PSMO-7 film in the field of magnetic refrigeration.

Emergent phenomena at interfaces have been investigated intensely in pursuit of the next generation spintronics. In this work, we have integrated heterostructure consisting of paramagnetic (PM) metallic Pt and antiferromagnetic (AFM) insulator LaMnO 3 (LMO). High-quality Pt (3 nm)/LMO (100 nm) heterostructure has been obtained by pulsed laser deposition. The structure, lattice strain and magnetic properties of epitaxial Pt/LMO heterostructure are fully studied. Due to the high sensitivity of synchrotron radiation and the high quality of epitaxial layer, the reflection intensity of the 3 nm-thick ultrathin Pt layer and LMO layer can be detected, and then lattice strain can be calculated. The LMO layer is under relative large tensile strain (2.13%), while the Pt layer is under relative small compressive strain (-0.46%). Magnetization measurements suggest that unexpected ferromagnetic behavior is observed clearly in the PM-Pt/AFM-LMO heterostructure. Moreover, spin glass (SG) state and exchange bias (EB) is also observed in this heterostructure. SG state is observed as a result of competing magnetic orders and spin frustration at the Pt/LMO interface. The heterostructure shows the EB effect below blocking temperature ( T B ), which is much lower than the Néel temperature ( T N ) of LMO, suggesting that the EB is strongly related to the SG state. The EB originates from the coupling between the SG and AFM phases., (© 2021 IOP Publishing Ltd.)

The geometric, optical, and magnetic properties of the M@Sn(12) clusters (M=Ti, V, Cr, Mn, Fe, Co, Ni) are studied using the relativistic density-functional method. The geometric optimization shows that the ground states of these clusters are probably very close to the I(h) structure. Our calculations demonstrate that the optical gaps of the M@Sn(12) can be tuned from infrared to green, and the magnetic moments of them vary from 2 mu(B) to 5 mu(B) by doping d transition metal atoms into Sn(12) cage, suggesting that M@Sn(12) could be a new class of potential nanomaterials with tunable magnetic and optical properties.