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Orbital currents play a fundamental role in a wide range of transport phenomena. Recently, the discovery of a novel chiral orbital current state in the ferrimagnetic nodal-line semiconductor Mn3Si2Te6 has attracted significant interest, supported by anomalous I–V characteristics and time-dependent bistable switching. However, the direct experimental verifications, combining electrical transport and magnetic measurement, that detect the variation of the magnetic properties vs the current are still rare. Here, we investigate the transport properties of Mn3Si2Te6 and track the current-induced dynamics of the magnetic moment. Reflective magnetic circular dichroism reveals that significant alterations in Mn3Si2Te6 magnetoresistance in response to an electric field are necessarily coupled with a magnetic phase transition, establishing a rare correlation. Our findings indicate the predominance of magnetic chiral orbital currents in the colossal angular magnetoresistance effect, offering a unique platform for advanced studies in orbital magnetism. [ABSTRACT FROM AUTHOR]

Fe doped Sr 2 RuMnO 6 (SRMO) double perovskites (Sr 2 RuMn 1-x Fe x O 6 , x = 0, 0.1, 0.2 and 0.3) were prepared by solid-state route. Both x-ray diffraction and Raman spectroscopy were performed to investigate the crystal structure of the synthesized double perovskites. Rietveld refinement of the x-ray diffraction patterns confirmed a phase transition from tetragonal to cubic space group as a function of doping concentration of iron. Raman spectroscopy at room temperature and group theory analysis revealed the phonon modes associated with the space group of the samples. The temperature dependent Raman spectroscopy showed an anharmonic behaviour of the phonon modes of the Fe doped SRMO samples. The temperature evolution of the phononic modes in the range of 300 K–620 K is predominantly influenced by the lattice degrees of freedom. The presence of several oxidation states Mn (2+, 3+ and 4+) and Fe (3+ and 4+) was confirmed by an X-ray photoemission spectroscopy analysis of the highest doped sample (x = 0.3). The magnetic properties measurements showed that the samples were completely paramagnetic at room temperature. The samples exhibit antiferromagnetism at very low temperatures and we conclude that they exhibit ferrimagnetic ground state in the mid temperature region. [ABSTRACT FROM AUTHOR]

A Z1-type Fe 3 Pd alloy with negative enthalpy of formation at ambient pressure has been discovered recently, however, its physical properties under high pressures remain unclear. In this work, the effect of pressure on the magnetic, electronic, lattice dynamic, mechanical and thermal properties of the Z1-Fe 3 Pd are investigated thoroughly by the first-principles methods. Under high pressures, the Z1-Fe 3 Pd are energetically favorable compared to other types Fe 3 Pd structures. A pressure-induced magnetic phase transition from ferromagnetic (FM) to ferrimagnetic (FIM) state are found, and the FM and FIM states are dynamically and mechanically stable under high pressures. The electronic density of states for both the FM and FIM states are analyzed to understand their magnetism. These two magnetic configurations are ductile, but their elastic properties and anisotropy are quite different. Additionally, the FM and FIM states have high uniaxial magnetocrystalline anisotropy, the FM state is a semi-hard magnet, and the FIM state undergoes a transition from hard magnet to semi-hard magnet with pressure. Finally, the volume and linear thermal expansion coefficients under high pressure are calculated, and the anisotropy of thermal expansion is also discussed in detail. • A stable Fe 3 Pd structure under high pressure is discovered for the first time. • The pressure-induced magnetic phase transition from ferromagnetic to ferrimagnetic state is determined. • The structural stability is verified by formation enthalpy, phonon and elastic. • Elasticity, thermal expansion and their anisotropies are investigated. • Ferrimagnetic state transforms from a hard magnet to a semi-hard magnet under high pressure. [ABSTRACT FROM AUTHOR]

This work utilizes a multi-scale computational approach combining first-principles density functional theory (DFT) and Monte Carlo statistical simulations to provide fundamental insights into the impacts of vanadium (V) doping on the structural, electronic, magnetic, and thermodynamic properties of wurtzite zinc sulfide (ZnS). 2 × 2 × 2 ZnS supercells with controlled V doping concentrations from 12.5%–25% substituting zinc sites were constructed. The introduction of V dopants induces systematic expansions in lattice parameters and cell volume, attributed to the larger ionic radius of V 2 + than Zn 2 + , while the average compressibility shows minimal variation. However, V incorporation is found to soften ZnS by over 15% at higher dopant contents, increasing compliance and anisotropy. Stable ferromagnetic spin couplings emerge, mediated by host carriers without precipitating V secondary phases. The band structure develops half-metallic electronic properties with the lifting of spin degeneracy and preferential spin-up band metallicity induced by V-3d and S-3p hybridization effects. This results in 100% spin polarization at the Fermi level. Monte Carlo simulations based on a tight-binding Hamiltonian constructed from maximally localized Wannier functions to accurately calculate the exchange interactions between V spins successfully reproduce the magnetic phase transition behavior. The results confirm high Curie temperatures exceeding 300 K at 25% V, attributable to the significant strengthening of short-range ferromagnetic couplings over antiferromagnetic interactions. The integrated computational approach provides fundamental insights into the microscopic origin of carrier-mediated ferromagnetism in V-doped wurtzite ZnS dilute magnetic semiconductors. The systematic first-principles calculations and statistical mechanics modeling establish clear structure–property relationships linking V doping configurations and concentrations to tuned mechanical response, enhanced stability, electronic structure modifications, spin polarization, and magnetic ordering temperatures in ZnS. The results present design pathways and predictive capabilities to guide experimental efforts toward emerging high-performance magnetic materials for spintronic technologies. [Display omitted] [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) ferromagnets with high Curie temperature TC are desirable for spintronics applications. However, they are rarely obtained in experiments mainly due to the challenge of synthesizing high-quality 2D crystals, and their TC values are below room temperature. Using first-principles calculations, we design a family of stable 2D FenGeTe2 (4 ≤ n ≤ 7) ultrathin films with coexisting itinerant and localized magnetism. Among them, 2D Fe3GeTe2 and Fe4GeTe2 are ferromagnetic metals with TC = 138 and 68 K; 2D Fe5GeTe2, Fe6GeTe2, and Fe7GeTe2 are Néel's P-, R-, and R-type ferrimagnetic metals with TC = 320, 450, and 570 K. A thickness-induced magnetic phase transition originates from competition between itinerant and localized states, and also correlates with Fe3+ and Fe2+ content. A valence/orbital-dependent magnetic exchange model is proposed for these effects. Our results reveal a universal mechanism for magnetic coupling in complex magnetic systems. 2D magnetism offers the prospect of ordered and controllable magnetic states at reduced dimensions and there is a desire to obtain materials which can realise these properties at room temperature. Here, the authors use first-principles calculations to demonstrate that a family of 2D FenGeTe-based ultrathin films with varying Fe content can exhibit a range of magnetic properties at elevated temperatures. [ABSTRACT FROM AUTHOR]

Z-type hexagonal ferrites have recently received attention for their room-temperature magnetoelectric (ME), which is activated when the temperature at which the transverse-conical spin-state transitions to a ferrimagnetic state is increased. The changes in the magnetic domain structure at the transition have been well-documented; however, they are still not understood in detail. In the present study, Lorentz transmission electron microscopy (TEM) analysis combined with an in situ heating experiment was conducted to demonstrate the shift in magnetic domain structure during the transition from the transverse-conical spin arrangement to a ferrimagnetic spin order. The dynamics of the magnetic domain structure changes with the increasing temperature were acquired in real-time. At 490 K, the magnetization transition from the transverse-conical spin state to the ferromagnetic state was demonstrated. Cross-tie domain walls formed during the magnetic transition process. The increased effect of the demagnetizing field applied to the 180° magnetic domains was caused by a lower magnetocrystalline anisotropy (MCA) at the easy axis of magnetization. [ABSTRACT FROM AUTHOR]

Samples with inversion parameter values (δ) ranging from 0.27 to 0.14 while maintaining the crystallite size value have been successfully fabricated from commercially available powders by mechanical grinding and thermal annealing treatments at temperatures ranging between 400 and 600 °C. Detailed characterization studies of these samples using X-ray, neutron diffraction and magnetic measurements have confirmed for the first time the simultaneous coexistence at 2 K of short range antiferromagnetic and ferrimagnetic ordering for a wide range of the inversion parameter. The magnetic phase diagram obtained is different from the one previously reported, which shows at 2 K the coexistence of long range antiferromagnetic order and short range order for values of inversion parameters less than 0.1 and the presence of a ferrimagnetic order only for values of δ > 0.2. At room temperature, the Rietveld analysis of NPD patterns and the magnetization curves showed a paramagnetic behavior in the samples with δ ≤ 0.1. For the samples with higher cationic inversion, typical hysteresis curves of ferrimagnetic materials were observed and the saturation magnetization values obtained agree quite well with the net magnetic moment obtained from the Rietveld refinement of the neutron diffraction patterns. [ABSTRACT FROM AUTHOR]

The contradictory relationship between magnetism and ductility restricts further applications of FeCoV alloys in high-performance electrical machines. The role of the BCC-B2 transition, accompanied by vanadium (V) site occupancies, in magnetic moments and ductility has been explored using first-principles calculations. The variations in magnetism and ductility of FeCoV alloys are attributed to the coupling of the BCC-B2 transition and V occupancies. When V replaces Fe atoms in the equiatomic B2-FeCo alloy, the superior magnetism observed in B2-Fe 50- c Co 50 V c alloys is a consequence of the enhanced local magnetic moment of Fe and the ferrimagnetic-ferromagnetic transition in the magnetic state. Moreover, due to the preferential V occupancy in the B2 phase, the B2-Fe 46 Co 50 V 4 alloy exhibits comparable ductility to the BCC-Fe 50 Co 46 V 4 alloy. The results indicate that the increased brittleness in the B2 phase arises from the raised Peierls stress and the enhanced covalent component in interatomic bonding, which is caused by the strong hybridization between Fe and Co atoms. Pearson correlation analysis illustrates that valence electron concentration (VEC) and V content are significant factors in the contradictory relationship between magnetization and ductility. The theoretical results demonstrate that tuning the V content and atomic occupancies is helpful to achieve a trade-off between magnetization and ductility in B2-FeCoV alloys. • The coupling effect of the BCC-B2 transition and V occupations on magnetic moment and ductility. • The underlying origins of magnetism-ductility contradictory relationship. • A trade-off between magnetic moment and ductility can be obtained in B2-Fe 46 Co 50 V 4 alloy. • the magnetization can be improved by adjusting VEC and V content. [ABSTRACT FROM AUTHOR]

Exploring valley-contrasting physics in scarce intrinsic high-temperature ferromagnetic semiconductors with feasible synthesis route is of great significance for ever-evolving moden information technology. By first-principles calculations, the TiInTe 3 monolayer is predicted to demonstrate excellent structural stability and easy-plane semiconducting ferromagnetism arising from indirect superexchange mechanism. Monte Carlo simulations based on the Heisenberg model reveal a magnetic phase transition at 583 K well above room temperature. Due to the inversion and time-reversal asymmetries, tunable valley polarization in the conduction band up to 110 meV can be achieved by varying the magnetization orientation, which is further validated by a first-order perturbation theory. More excitingly, electron doping for realizing the anomalous valley Hall effect gives rise to an out-of-plane preference for magnetization in the TiInTe 3 monolayer and thus generates spontaneous and larger valley polarizations. After doping, the ferromagnetism above room temperature remains robust in the experimentally attainable electron density regime. Our findings highlight that the TiInTe 3 monolayer is a promising ferrovalley material for developing high-performance spintronic and valleytronic nanodevices. [Display omitted] [ABSTRACT FROM AUTHOR]

Peltier effects, which produce a heat flux at the junction of two different materials, have been an important technology for heating and cooling by electrical means. Whereas Peltier devices have advantages such as cleanliness, silence, compactness, flexibility, reliability, and efficiency, relatively complicated modular structures are unavoidable, leading to a higher cost than that of commonly used refrigeration technology. Here, we provide a concept of a Peltier device composed of a single magnetic material exhibiting a first-order magnetic transition. Our concept is based on a controllable junction structure consisting of two magnetic phases with opposite Peltier coefficients instead of a semiconductor junction. Using Mn 1.96 Cr 0.04 Sb samples with the first-order magnetic transition between ferrimagnetic (FI) and antiferromagnetic (AF) states, we successfully made a stable junction structure of AF/FI/AF by a pulse heating method and achieved a maximum Peltier coefficient of 0.58 mV. Our device concept was further verified by a numerical simulation based on a finite element method. The single-material Peltier effect reported here avoids a complex device design involving material junctions and is importantly reconfigurable. [ABSTRACT FROM AUTHOR]

Using ab-initio calculations, the electronic and magnetic properties of double perovskite oxide Sr 2 CrReO 6 with two type of strains: biaxial (along the [110]-direction) and hydrostatic (along [111]-direction) are investigated. The ground state of the unstrained system is half-metallic ferrimagnetic, due to a strong antiferromagnetic (AFM) coupling between Cr and Re atoms within both (GGA and GGA+U) exchange-correlation potentials. It is demonstrated that the robustness of half-metallicity can be preserved under the influence of both biaxial and hydrostatic strains. Interestingly, a transition from ferri-to-ferromagnetic is established due to Re spin flipping to that of the Cr ion (i.e. Cr and Re spin becomes parallel) within the GGA+U method for both biaxial and hydrostatic tensile strains of ≥ + 2 % . The strong confinement of orbitals due to tensile strain results in the decrease of electron hopping which further reduced the AFM coupling strength between Cr and Re atoms, this leads to a ferri-to-ferromagnetic transition. However, the GGA scheme holds the ferrimagnetic state with both kinds of strains. This work shows that tensile strain is a feasible way to optimize the magnetic properties of perovskite oxides, which are presumed to be beneficial for spintronic technology. [ABSTRACT FROM AUTHOR]

We prepared pure-phase Ni x Mn 1-x Co 2 O 4 (x = 0, 0.25, 0.5, 0.75 and 1) nanoparticles using a low-temperature solid-state reaction method. Magnetization measurement results showed that with Ni doping, the Curie temperature and coercivity of Ni x Mn 1-x Co 2 O 4 increased. Multiple magnetic phases that transition from paramagnetic to ferrimagnetic to ferrimagnetic and antiferromagnetic were observed to coexist in the Ni 0.5 Mn 0.5 Co 2 O 4 sample. At low temperatures, the ferromagnetic and antiferromagnetic phases coexist in Ni x Mn 1-x Co 2 O 4 (x = 0 and 0.25), and as the concentration of Ni increases, Ni x Mn 1-x Co 2 O 4 (x = 0.75 and 1) show a spin glass state. The structure of Ni x Mn 1-x Co 2 O 4 (x < 0.5) is mainly affected by cation defects, and by cation substitution when x is greater than 0.5. The results of first-principles calculations show that covalent bonds exist in Ni x Mn 1-x Co 2 O 4 and that the strength of the Ni-O bond is greater than that of the Mn-O bond. [ABSTRACT FROM AUTHOR]

Here, we report structural and magnetic phase transitions in NiCr 1.9 Fe 0.1 O 4 nanoparticles of size ∼60 nm synthesized through cost-effective co-precipitation route. X-ray diffraction pattern shows a stable cubic phase at RT in contrast to tetragonal phase in bulk NiCr 2 O 4. Decreasing the temperature, a complete tetragonal symmetry is observed at 50 K, while a coexistence of cubic and tetragonal phases in the intermediate temperature range. Interestingly, no tetragonal to orthorhombic phase transformation has been observed down to 12 K as observed in NiCr 2 O 4 at 70 K. The local structure examined from temperature dependent EXAFS demonstrates that although no change in distribution of cations among tetrahedral (A) and octahedral (B) sites down to 10 K has been observed, Fe3+ ions occupy A site replacing equivalent amount of Ni2+ towards B site which is contradicting to the bulk NiCr 2 O 4 where Ni2+ occupies only A site. Magnetic studies demonstrate a two-fold increase in para to long-range ferrimagnetic transition, T C , due to increase in A-B exchange interaction and no change in spiral ordering temperature, T S indicates strong B-B interaction. In addition, these nanoparticles exhibit unusually high spontaneous exchange bias of ∼1.265 kOe at 60 K. We discuss the temperature dependent exchange bias on the basis of competition between uncompensated B site moments and ferromagnetically ordered spins at A site. The tunable exchange bias without field highlight the potential applications of these materials in spintronics devices. [ABSTRACT FROM AUTHOR]

The magnetic structure of La 1- x Tb x Mn 2 Si 2 compounds with 0 ≤ x ≤ 1 has been studied by powder neutron diffraction and magnetization measurements on single-crystal samples. We demonstrate that at 4.2 K, with increasing the Tb concentration, a canted ferromagnetic structure of LaMn 2 Si 2 changes at x > 0.2 to a canted antiferromagnetic structure. The antiferromagnetic in-plane component of Mn moment decreases with increasing concentration x and vanishes at x > 0.5. TbMn 2 Si 2 is characterized by a collinear in-plane Mn ordering and ferrimagnetic structure, in which the Mn sublattice possesses the ferromagnetic interlayer alignment along the easy c -axis. Neutron diffraction study does not reveal a long-range magnetic order of Tb moments for the compounds with x ≤ 0.4. Our results show that for concentrations 0.2 < x ≤ 0.4, a competition of the interlayer Tb-Mn, Mn-Mn exchange interactions and strong uniaxial magnetic anisotropy leads to formation of a frustrated magnetic state of Tb ions, which prevents magnetic ordering in the Tb sublattice. [ABSTRACT FROM AUTHOR]

Bulk CoCr2O4 undergoes a transition from paramagnetic to long-range ferrimagnetic phase at Tc (94 K) to a long-range and/or short-range spiral order at Ts ( \sim 24 K), and finally shows a lock-in-transition below 15 K. The spiral component induces an electric polarization and also a spontaneous magnetization for which it is said to be multiferroic. Reducing the size of a CoCr2O4 multiferroic material to \sim 50 nm by a coprecipitation method, we obtain a pure cubic phase with space group, Fd3m and lattice parameter (8.334 ± 0.003 °A). A rich sequence of magnetic transitions are examined by measuring temperature and field-dependent magnetization and diffused neutron scattering (DNS) using polarized neutron at different temperatures. While paramagnetic to ferrimagnetic transition is enhanced from 97 K in bulk to 99 K at 0.5 kOe field, followed by a decrease in lock-in-transition ( TL ) from 15 K in bulk to 8 K, spiral ordering temperature does not show a significant change. A strong disagreement between paramagnetic moment obtained from the fitting of \chi ^{-1}=({T}/{C})+({1}/{\chi o})-({b}/{T-\theta }) and ferrimagnetic moment obtained from the $M$ versus H$ loop taken at 2 K, nonsaturated magnetization at 50–100 kOe field, two order of magnitude higher coercivity ( H_{c} ), and splitting of ac susceptibly confirm the core–shell structure of the particles. Furthermore, a magnetic scattering analysis clearly shows that while the paramagnetic to ferrimagnetic transition is continuous, the spiral ordering is sharp, short range, and commensurate in contrast to incommensurate spiral order observed single crystal of CoCr2O4. [ABSTRACT FROM PUBLISHER]

The ferrimagnetic Mn2−xCoxSb ( $x$ = 0.15 and 0.20) alloys were prepared by arc-melting technique. The structure, magnetic, and magnetocaloric properties on these compounds were investigated. The tetragonal Cu2Sb-type structure ( $P$ 4/nmm space group) was confirmed by X-ray powder diffraction measurements at room temperature for these two alloys. The Co-introduction results in a first-order magnetic transition between the antiferromagnetic and the ferrimagnetic state. Adopting the standard and loop process method, respectively, the measurements of isothermal magnetization were performed and the magnetic entropy changes were evaluated for these alloys. [ABSTRACT FROM AUTHOR]

• The mechanical alloying reduced the sintering temperature to stabilize orthorhombic phase. • The site occupancy of Fe and Ga ions controlled ferrimagnetism, soft and hard magnetic phases. • The low temperature magnetic peak appeared due to magnetic frustration and anisotropy. • The extra moment with reference to spin value suggested contribution for orbital moment. • The ferrimagnetism and spin-phonon coupling indicated multiferroelectric nature in the system. A combined technique of mechanical alloying and heat treatment has been used to prepare the polycrystalline samples of Fe 2−x Ga x O 3 (x = 0.6–1.2) system in orthorhombic phase. It has been possible to reduce the sintering temperature by ~350 °C for stabilizing the orthorhombic phase in comparison to the temperature reported in literature. The Rietveld refinement of X-ray diffraction patterns indicated the distribution of Ga and Fe atoms in the Ga1, Ga2, Fe1 and Fe2 sites of the lattice structure. A linear variation of the lattice parameters with Ga/Fe content showed application of Vegard's law. The temperature-dependent magnetization measurements confirmed ferrimagnetic order of Fe spin moments. The ferrimagnetic transition temperature (T C) has decreased from 320 K to 100 K with the increase of Ga content in the range of x = 0.6–1.2. Temperature-dependent Raman spectroscopy data ruled out any structural phase transition at T C , but an anomalous behaviour of the position and width of the peaks of Raman active phonon modes near to T C confirmed a strong spin–phonon coupling in the material. The spin–phonon coupling strength (η) for the A9 mode has been found around 1.64 cm−1 for x = 1 and 3.34 cm−1 for x = 0.8, and η for the A21 mode has been found around 2.12 cm−1 for x = 1 and 3.28 cm−1 for x = 0.8. The spin-phonon coupling strength has been diluted in the samples with higher content of Ga. The experimental results indicated that the variation of Ga/Fe content and its distribution in lattice sites determine the ferrimagnetic properties, magnetic anisotropy and spin-phonon coupling in Fe 2−x Ga x O 3 system. The results are expected to be useful for understanding the spin-phonon coupling in multiferroic-magnetoelectric materials with magnetic and electric transitions near to room temperature. [ABSTRACT FROM AUTHOR]

Abstract: Large sized α-Li3Fe2(PO4)3 single crystals with high quality are successfully grown by a flux method. Magnetic behaviors of the grown crystals are investigated by means of magnetic susceptibility, magnetization, and heat capacity measurements along different directions. The results confirm that α-Li3Fe2(PO4)3 exhibits weak ferrimagnetic behaviors at low temperature, which are in good agreement with those reported previously. However magnetic anisotropy is confirmed for the first time, suggesting that the c-axis is the likely magnetic easy axis and the a-axis is the magnetic hard one. Two anomalies are clearly observed in magnetic susceptibility along the a-axis and heat capacity data at zero field, suggesting the appearance of two successive magnetic transitions at ~26 and ~22K in the system. [Copyright &y& Elsevier]

Abstract: This paper presents a review and results of comparative study of the influence of Gd on some physical properties of (R 0.9 R′0.1)1−x Gd x Co2 solid solutions with R=Dy, Ho and R′=Er, Ho and x varied from 0.05 to 0.15. Powder X-ray diffraction analysis performed at room temperature revealed that all studied solid solutions solidify with the formation of a Laves-phase MgCu2-type structure (space group Fd−3m). The magnetization behavior and the magnetic transition are analyzed in terms of the Landau theory. The studies of magnetic properties and heat capacity showed that a relatively small Gd addition significantly increases T C of the compounds. The maximum percentage increase in T C, namely, ~43% was observed for (Ho0.9Er0.1)1−x Gd x Co2. However, the highest temperature was noted for the (Dy0.9Ho0.1)0.85Gd0.15Co2 solid solution; it is T C=183.4K. Below the ordering temperature, all samples are ferrimagnetically ordered; at high temperatures, they are Curie–Weiss paramagnets. Moreover, a small Gd addition eliminates the field-induced magnetic transition near T C and, as consequence, transforms the nature of magnetic transition from the first- to second-order. The magnetocaloric effect has been estimated in terms of both isothermal magnetic entropy and adiabatic temperature changes. The highest adiabatic temperature change ΔT ad=3K and highest isothermal entropy change ΔS mag=12.1J/kgK were observed for (Ho0.9Er0.1)0.95Gd0.05Co2 at ~90K in magnetic fields of 2T and 3T, respectively. A decrease in the entropy change has been observed with increasing Gd content in all studied samples. The smallest values of ΔS mag were observed for the (Dy0.9Ho0.1)1−x Gd x Co2 solid solutions. Under an external field change of from 0 to 3T, the maximum entropy change for (Dy0.9Ho0.1)1−x Gd x Co2 compounds decreases from 6.9at x=0.05–4.3J/kgK at x=0.15. The refrigerant capacity for all solid solutions (with 0.05≤x≤0.15) is reported. The effect of increasing Gd content in the solid solutions on their magnetic and magnetocaloric properties is discussed. [Copyright &y& Elsevier]

Abstract: A magnetic phase diagram of Fe1−х Zn х Cr2S4 solid solutions was studied. The temperature and concentration ranges of existence of magnetoactive phases based on ferrimagnet FeCr2S4 (0≤х≤0.63), antiferromagnet ZnCr2S4 (0.73≤х≤1), and a spin glass (0.63≤х≤0.73) were determined. The concentration dependences of the saturation magnetic moments and Curie temperatures of the solid solutions synthesized were investigated experimentally and theoretically. [Copyright &y& Elsevier]

• Synthetic and biogenic ferrihydrite nanoparticles are synthesized. • Analysis of the Mössbauer spectra and magnetometry revealed the interparticle magnetic interactions in synthetic ferrihydrite. • Collective processes of freezing the magnetic moments of particles take place in synthetic ferrihydrite. Samples of synthetic ferrihydrite with an average nanoparticle size of 2.7 nm have been examined by magnetometry and Mössbauer spectroscopy. Ferrihydrite is characterized by the antiferromagnetic interactions between the magnetic moments of iron atoms. In ferrihydrite nanoparticles, as in any other antiferromagnetic ones, structural defects induce the formation of an uncompensated magnetic moment, which determines the magnetic properties typical of single-domain ferro- and ferrimagnetic particles. The manifestation of the magnetic interactions between ferrihydrite nanoparticles in the magnetic properties of the material and in the temperature evolution of Mössbauer spectra has been in focus. The results obtained on synthetic ferrihydrite have been compared with the data for the biogenic ferrihydrite sample with a similar average size of particles surrounded by a polysaccharide shell, which weakens and screens the interparticle magnetic interactions. A clear manifestation of the effect of the interparticle magnetic interactions on the transition to the blocked state is the presence of a significant contribution of the relaxation component in the Mössbauer spectra at temperatures of the transition from the superparamagnetic to blocked state. The temperature dependence of the particle relaxation time obtained from the Mössbauer spectra points out the collective effect of freezing of the magnetic moments of particles due to the magnetic interactions between them. [ABSTRACT FROM AUTHOR]

Among the double perovskite oxides, Sr 2 CrReO 6 has been attractive a lot of attention due its half-metallic ferrimagnetic nature and the highest magnetic transition temperature of 635 K. Here, we systematically investigated the influence of uniaxial strain along [100]-direction on the electronic and magnetic properties of double perovskite oxide Sr 2 CrReO 6 using first-principle calculations. Our results show that a critical tensile strain of + 2% leads the system to the ferromagnetic metallic state from half-metallic ferrimagnetic with a spin-polarization of 64%. Because, tensile strain decreases the anti-ferromagnetic coupling between Cr and Re ions, which results in ferromagnetic ordering. The admixture of Cr/Re d x 2 − y 2 , d x z , and d y z orbitals are mainly responsible for metallicity. Along with this, the total magnetic moment gets enhanced and almost close to an integral value of 5 μ B for higher tensile strains. On the other hand, compressive strains exhibit no substantial impact on the physical properties of Sr 2 CrReO 6. Moreover, it is also found that spin-polarization optimized with a further increase of tensile strains. Close to half-metallic ferromagnetic state due to tensile strain, this material shows a wide range of scientific and technological applications in spintronics. • Antiferromagnetic superexchange coupling leads the system to ferrimagnetic ground state. • A magnetic phase transition from half-metal ferrimagnetic to ferromagnetic metal occurs for +2% uniaxial strain. • Spin-polarization enhanced for tensile strains. [ABSTRACT FROM AUTHOR]

Effects of Manganese (Mn) substitution on the magnetic and dielectric properties of spinel phase Co 1−x Mn x Cr 2 O 4 (0.0 ≤ x ≤ 1) nanoparticles (NPs) have been studied. X-ray diffraction and Fourier transform infrared spectroscopy analysis showed the normal spinel structure for all the samples. Average crystallite size showed increasing trend with Mn doping and lies in the range 32–47 nm. The undoped CoCr 2 O 4 NPs displayed a typical phase transition from paramagnetic (PM) to ferrimagnetic (FiM) state at T C = 100 K along with conical spiral magnetic state at T S = 27 K and lock-in transition state at T L = 13 K. The T C , T S and T L values were shifted towards lower temperatures with increasing Mn content and finally an antiferromagnetism (AFM) is obtained for MnCr 2 O 4 NPs at T N = 20 K. A magnetic phase diagram was developed which showed the presence of different phases in these nanoparticles and attributed it to change in magnetic interactions with increasing Mn content. Saturation magnetization (M S) showed an increasing trend with Mn content due to the large magnetic moment of Mn ions. Nanoparticles showed an overall increasing trend of the dielectric constant with Mn concentration which is due to possible hopping of Mn2+ to Mn3+ and as well as increasing average crystallite size with Mn doping. In summary, increase in Mn doping revealed reduction in T C , T S , and T L values, an increasing M S trend, an AFM phase introduction and improved dielectric properties for Co 1−x Mn x Cr 2 O 4 NPs. Image 1 • Magnetic transitions shifted towards lower temperature regime with Mn content. • Non-collinear spin contribution produced AFM transition in pure MnCr 2 O 4 NPs. • Smaller magneto-crystalline anisotropy decreased the H C of pure MnCr 2 O 4 NPs. • Possible oxidation in Mn and crystallite size increased the dielectric constant. [ABSTRACT FROM AUTHOR]

We report on the crystal structure and the magnetic properties of Mn5Sn3-xGax alloys with x = 0.1, 0.3, 0.5, 1.0, and 1.5, which were investigated by means of X-ray powder diffraction and magnetization measurements in fields up to 5 T in the temperature range 5 to 360 K. These alloys have in common that they exhibit a temperature-induced ferrimagnetic phase transition. The results indicate that all samples crystallize in the hexagonal Ni2 In-type structure with space group P63/mmc. The lattice parameters a and c of the Mn5Sn3-xGax decrease with increasing x, while the Curie temperature of these alloys increases with increasing x. All of the alloys exhibit a moderate magnetocaloric effect. Typical values are about 0.8 and 3 J/kgK at Tc = 282 K for x = 1.5 in a magnetic field change from 0 to 1 T and 0 to 5 T, respectively. [ABSTRACT FROM AUTHOR]

The magneto–elastic coupling effect correlates to the changes of moment and lattice upon magnetic phase transition. Here, we report that, in the pseudo-binary Laves-phase Tb1-xDyxCo2 system (x = 0.0, 0.7, and 1.0), thermal expansion and magnetostriction can probe the ferrimagnetic transitions from cubic to rhombohedral phase (in TbCo2), from cubic to tetragonal phase (in DyCo2), and from cubic to rhombohedral then to tetragonal phase (in Tb0.3Dy0.7Co2). Furthermore, a Landau polynomial approach is employed to qualitatively investigate the thermal expansion upon the paramagnetic (cubic) to ferrimagnetic (rhombohedral or tetragonal) transition, and the calculated thermal expansion curves agree with the experimental curves. Our work illustrates the correlation between crystal symmetry, magnetostriction, and thermal expansion in ferrimagnetic Laves-phase alloys and provides a new perspective to investigate ferrimagnetic transitions. [ABSTRACT FROM AUTHOR]