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• Ti2MnAl crystallizes with significant atomic disorder resulting in random mixing of constituent elements. • Atomic disorder plays an important role in determination of physical properties. • Ti2MnAl exhibits Pauli's paramagnetic behaviour. • Non-interacting superparamagnetic clusters emerge at low temperatures due to defects. • Disorder give rise to a negative temperature coefficient of resistivity. Search for novel spintronic materials in family of Heusler alloys has attained significant interest in recent years. In this context, Ti 2 MnAl is interesting as it is predicted to host spin gapless semiconducting state and compensated ferrimagnetic ordering. Here we report a detailed experimental investigation of Ti 2 MnAl. Our studies reveal that Ti 2 MnAl crystallizes in cubic structure with strong atomic disorder along with Pauli paramagnetic behaviour. The influence of disorder manifests in form of non-interacting superparamagnetic clusters at low temperatures and negative temperature co-efficient of resistivity. The carrier concentration obtained from Hall resistivity rules out the possibility of spin gapless semiconducting state. Our studies indicate that atomic disorder plays an important role in determination of physical properties of Ti 2 MnAl. [ABSTRACT FROM AUTHOR]

We investigate the finite temperature properties of the mixed spin-1/2 and spin-1 ferrimagnetic chain with both longitudinal single-ion anisotropy D z and transverse single-ion anisotropy D x. The spin excitation spectrum as well as the thermodynamic quantities are explored by means of the Villian transformation theory. We find two branches of the low-lying energy spectrum are strongly dependent on the model Hamiltonian parameters J 1 , J 2 , D z , D x. Our results agree well with the exact method results for the mixed spin-1/2 and spin-1 Ising chain. The thermodynamic quantities of XY ferrimagnetic spin- (1 / 2 , 1) chain varying with D z and D x , such as free energy, internal energy, entropy, specific heat and magnetization are explicitly discussed, respectively. The result shows that the magnetization plateaux exists in XY ferrimagnetic spin chain without anisotropy, which indicates a phase transition may occur in XY ferrimagnetic spin chain. • The thermodynamic properties of the XY ferrimagnetic spin- (1 / 2 , 1) chain are investigated. • One branch of the energy spectrum for XY ferrimagnetic spin- (1 / 2 , 1) chain is omega-shape, which is different from XYZ mode. • The magnetization plateau exists for XY ferrimagnetic spin- (1 / 2 , 1) chain and it is independent of anisotropy. [ABSTRACT FROM AUTHOR]

In this work, the exchange bias behavior and magnetocaloric effect have been studied in Mn 7 Sn 4 alloy. The X-ray powder diffraction pattern recorded at room temperature indicates that the sample crystallizes in a single phase with Ni 2 In-type hexagonal structure (space group P 6 3 / mmc). The maximum magnetic entropy change value across paramagnetic/ferrimagnetic transition is about 3.3 J kg−1 K−1 under the magnetic field change of μ 0 Δ H = 0 - 5 T. With further cooling, the reentrant spin-glass-like state is obtained below 150 K, for which the exchange bias effect has been observed. The exchange bias field is ∼7.8 mT and ∼6.7 mT at T = 10 K when the cooling field is μ 0 H CF = 0.1 T and 0.5 T, respectively. The magnetic behavior and the origin of exchange bias in Mn 7 Sn 4 are discussed. • The reentrant spin glass like state should be demonstrated by the multiple steplike anomalies. • The magnetocaloric and exchange bias effects are studied. • Interfacial coupling between ferrimagnetic and RSGL state is believed as the origin of EB effect. [ABSTRACT FROM AUTHOR]

Abstract The magnetic properties of tetragonal structure of stoichiometric NiMn alloy is investigated using density functional theory within the local spin density approximation. The system studied here, is a free standing film. The effect of thickness and epitaxial strain on the magnetic and structural properties is examined. It is found that while the magnetic moments of Mn surface atoms vary depending on the number of layers being odd (3.60 μ B) or even (3.55 μ B) the magnitude of the magnetic moment for surface Ni atoms is constant (0.11 μ B). By applying epitaxial strain on the slabs, it was observed, for the first time, that the magnetic phase of NiMn films changes from "A-type-like" ferrimagnetic for compressive strains to "G-type-like" ferrimagnetic for tensile strains. Highlights • Effect of thickness and epitaxial strain on the magnetic structure of NiMn films are investigated. • Surface buckling phenomenon for different thicknesses is studied. • A magnetic phase transition from A-type-like ferrimagnetic to G-type-like ferrimagnetic was observed by applying epitaxial strain. [ABSTRACT FROM AUTHOR]

Electronic transport and magnetic properties of bulk and rapid melt quenched samples of the Mn 3 Al Heusler alloy were studied. A correlation between the magnetic and structural states was established. For a cast sample, there is no ferromagnetic moment, and the behavior of the magnetic susceptibility (break at low temperatures and the Curie-Weiss law with high values of the paramagnetic Curie temperature) indicates a frustrated antiferromagnetic state. At the same time, for a rapid melt quenched sample, a ferrimagnetic state is observed with a moment close to compensation. The results of measurements of the electrical resistivity and the Hall effect evidence as well in favor of the implementation of these magnetic states. • Mn 3 Al in the initial cast state and after rapid melt quenching (RMQ) are studied. • Electronic transport and magnetic state are very sensitive to the structural state. • A cast alloy magnetic susceptibility is indicated a frustrated antiferromagnetism. • Ferrimagnetic state in RMQ sample is observed with a moment close to compensation. • Current carrier concentration and mobility are different for cast and RMQ alloys. [ABSTRACT FROM AUTHOR]

Based on the method of Dyson–Maleev mean-field theory, we study the Heisenberg ferrimagnetic spin chain at zero temperature. The energy spectrum exhibits the coexistence of a nearly gapless branch and a gapful branch. Compared with numerical results of other methods, the energy gap, Δ h = 1.32 , of Dyson–Maleev mean-field theory is reasonable and only a little bit lower. At finite temperature, the properties of energy gap, magnetization, uniform susceptibility, internal energy, specific heat are calculated respectively. The trends of these thermodynamic properties in this method are consistent with the existed results of other methods. [ABSTRACT FROM AUTHOR]

We investigate the ferrimagnetism and ferroelectricity of bulk NiFe 2 O 4 with tetragonal P 4 1 22 symmetry by means of density functional theory calculations using generalized gradient approximation + Hubbard U approach. Special attention is paid to finding the most energetically favorable configuration on magnetic ordering and further calculating the reliable spontaneous electric polarization. With the fully optimized crystalline structure of the most stable configuration, the spontaneous polarization is obtained to be 23 μC/cm 2 along the z direction, which originates from the hybridization between the 3d states of the Fe 3+ cation and the 2p states of oxygen induced by Jahn–Teller effect. [ABSTRACT FROM AUTHOR]

Using spin-polarized first-principles calculation, we investigate the structural, electronic and magnetic properties of the Zn 31 Co 1 S 32 , Zn 31 Ni 1 S 32 and Zn 30 Co 1 Ni 1 S 32 systems. The results show that the Zn 31 Co 1 S 32 system is a magnetic semiconductor, while the Zn 31 Ni 1 S 32 system exhibits a magnetic half-metallic (HM) character. The Zn 30 Co 1 Ni 1 S 32 system exhibits a HM ferrimagnetic character explained by the superexchange mechanism. The Co and Ni atoms favorably occupy nearest neighbor positions of the metal sublattice with antiparallel arrangement of their magnetic moments. Furthermore, it is observed that the magnetic moment of Co/Ni atom reduces from an isolated atom magnetic moment due to p–d hybridization which yields small parallel magnetic moments on the nearest S atoms. [ABSTRACT FROM AUTHOR]

Double perovskite oxide La 2 CrFeO 6 with the characteristic of ferrimagnetic insulator has been reported by Chakraverty and Lee et al. Engineering the physical properties of materials, including obtaining unusual properties, can be achieved by some measures, and defect-tuning has been one of the most efficient measures. Here, by using density-functional calculations, La vacancy is introduced in La 2 CrFeO 6 and special properties are obtained successfully. The results show that the magnetic phase of La 2 CrFeO 6 would transfer from ferrimagnetic to ferromagnetic ordering as long as La vacancy is introduced. Furthermore, La 1.75 CrFeO 6 shows direct spin gapless semiconductor, and La 1.5 CrFeO 6 behaves as half-metal with the half-metallic gap of 0.42 eV. In the whole range of La vacancy, the electronic configurations of both Cr and Fe ions exhibit high-spin states, the magnetic moment of Fe remains 4.20 μ B , while that of Cr ions decreases from 2.66 to 1.97 μ B with increasing the amount of La vacancy. This work opens an alternative way to design spintronic materials, especially for direct spin gapless semiconductors which have never been reported in perovskite oxides. [ABSTRACT FROM AUTHOR]

The bond operator theory is applied to study Heisenberg ferrimagnetic spin chain. We observe four branches of excited spectrum, the gap of excited spectrum and energy spectrum at T = 0 K . The energy gap is 1.64, which agrees quite well with the established numerical results. At finite temperature, the energy gaps, uniform susceptibility, internal energy and specific heat are calculated respectively. These results qualitatively agree with numerical results by other methods quite well. [ABSTRACT FROM AUTHOR]

In this research, the magnetic and optical properties of SrFe2O4 ceramic were studied. The calculations were performed by Full Potential Linearized Augmented Plane Wave method in Density Functional Theory framework with generalized gradient (GGA), GGA+U and modified Becke-Johnson approximations for the exchange and correlation functionals. The results show that SrFe2O4 is a ferrimagnetic ceramics with six different spin configurations. The Hubbard parameter was calculated (Ueff = 4.5 eV) by an ab initio method. The optical properties such as dielectric function, refraction index, electron energy-loss function, reflectivity, absorption coefficient and optical conductivity were investigated at zero up to 20 GPa pressure in x, y and z directions. The pressure coefficients of optical band, static dielectric constant, plasmon peak, static refraction index and the maximum of absorption were determined. Moreover, the pressure dependence of the static dielectric constant, plasmon peak, static refraction index, the maximum of absorption and the optical gap were investigated. [ABSTRACT FROM AUTHOR]

The local magnetism induced by vacancies in the presence of the spin-orbit interaction is investigated based on the half-filled Kane-Mele-Hubbard model on the honeycomb lattice. Using a self-consistent mean-field theory, we find that the spin-orbit coupling will enhance the localization of the spin moments near a single vacancy. We further study the magnetic structures along the zigzag edges formed by a chain of vacancies. We find that the spin-orbit coupling tends to suppress the counter-polarized ferrimagnetic order on the upper and lower edges, because of the open of the spin-orbit gap. As a result, in the case of the balance number of sublattices, it will suppress completely this kind of ferrimagnetic order. But, for the imbalance case, a ferrimagnetic order along both edges exists because additional zero modes will not be affected by the spin-orbit coupling. [ABSTRACT FROM AUTHOR]

Abstract: A fine structure of high-field magnetization curves of CsCoCl3 and related compounds is discussed. It is shown that a precursor of a high-field phase transition originates from nucleation of an intermediate high-field ferrimagnetic (IFM) phase. Since the IFM state is degenerate its growth starting from few nucleation centers gives rise to domain walls formation. Their creep also makes a contribution to the magnetization dynamics similar to slow relaxation in Ca3Co2O6. An experimental verification of the model is proposed. [Copyright &y& Elsevier]

• Dynamic phase transitions of the mixed spin (1/2, 3/2) system are investigated by the path probability method. • The system undergoes two successive phase transitions in some cases. • The system exhibits one or two dynamic tricritical and double critical end points. • The system contains the paramagnetic, ferrimagnetic and mixed phases. • The system displays reentrant behavior for certain interaction parameter. Dynamic phase transitions (DPTs) of the mixed spin (1/2, 3/2) Ising ferrimagnetic model on the two interpenetrating square lattice with the bilinear and crystal-field interactions under a time-varying (sinusoidal) magnetic field were examined by using the path probability method (PPM). We studied stationary solutions of dynamic average magnetizations and obtained phases and then we investigated thermal behaviors of dynamic magnetizations to designate the nature of the DPTs and find the DPT temperatures. We also constructed the dynamic phase diagrams (DPDs) in two different planes. DPDs exhibit the paramagnetic (p), ferrimagnetic (i), and mixed phases (i + p), and one or two dynamic tricritical points and dynamic double critical end points. The reentrant behavior is also seen. We observed that the PPM is a more appropriate dynamic method to study the dynamic features of ferrimagnetism. [ABSTRACT FROM AUTHOR]

• Intersubband interaction results in complicated spin texture and Berry curvature. • Coexistence of Rashba and Dresselhaus spin-orbit interactions flips Berry phase sign. • Heavy holes abruptly change their Berry phase signs because of the Rashba term. • Spin-orbit interactions break the pair relation between heavy holes. • Counting quasi-degenerate points determines the energy dependence of Berry phase. By extending the k ⋅ p approach, we study the spin texture and Berry phase of heavy-mass holes (HHs) confined in the SiGe two-dimensional (2D) quantum well system, focusing on the intersubband interaction via the coexistence of the Rashba and Dresselhaus spin-orbit interactions (SOIs). The coexistence of both SOIs generates spin-stabilized(+)/destabilized(-) HHs. The strong intersubband interaction causes quasi -degenerate states resembling the 2D massive Dirac fermion. Consequently, the Berry phases of HHs have unique energy dependence understood by counting the quasi -degenerate points with the signs of the Berry phases. Thermal averaging of the Berry phase demonstrates that HH + / − has a peculiar plateau of + π /− π at less than 30 K and then changes its sign at approximately 200 K. [ABSTRACT FROM AUTHOR]

• Ferrimagnetic mixed spin systems on body-centered cubic recursive lattice are studied exactly. • The existence of new intermediate phase is predicted in all investigated models. • The second-order nature of all phase transitions is shown and all phase diagrams are found. • All possible series of consecutive phase transitions are identified and discussed. • Magnetization properties of all phases of studied models are investigated in detail. Using the recursive lattice technique the existence of the intermediate phase, which separates two ferrimagnetic phases in the 1 / 2 − σ (σ = 1 , 3 / 2 , 2) mixed-spin Ising ferrimagnets with the presence of the next-to-nearest neighbor interaction on the regular body-centered cubic lattice, is predicted. It is shown that, for given spin value of the central sites of the body-centered cubic lattice, this intermediate phase is realized in the corresponding narrow interval of the values of the frustration parameter of the model, that the form of the region, where the intermediate phase exists, depends on the value of the central spin σ (becomes larger with increasing of σ), and that all transitions between various phases of the model always have the second order nature. All possible series of consecutive phase transitions of the model are identified and the properties of the sublattice magnetizations are studied and discussed in detail. [ABSTRACT FROM AUTHOR]

• We study a frustrated general spin-S Ising antiferromagnet on a kagome lattice. • We explore possibility of long-range ordering for any finite or infinite values of S. • Character of the spin-correlation function is studied by Monte Carlo simulations. • It is found that system remains disordered for any spin S and any finite temperature. The possibility of the emergence of some kind of long-range ordering (LRO) due to the increase of multiplicity of the local degrees of freedom (spin value S) is studied in an Ising antiferromagnet on a kagome lattice (IAKL) by Monte Carlo simulation. In particular, the critical exponent of the spin correlation function, obtained from a finite-size scaling analysis, is evaluated for various values of S , including S = ∞ , with the goal to determine whether there exists some threshold value of the spin S C above which the system would show true or quasi-LRO, similar to a related model on a triangular lattice (IATL). It is found that, unlike in the IATL case, the IAKL model remains disordered for any spin value and any finite temperature. [ABSTRACT FROM AUTHOR]

• Monte Carlo simulation has been performed to study the magnetocaloric properties of Sr 2 CrIrO 6. • Magnetic entropy change, adiabatic temperature change and relative cooling power have been calculated. • The hysteresis loops of the system are examined as a function of the model parameters. The hysteresis behavior and the magnetocaloric properties of the double perovskite (DP) S r 2 C r I r O 6 near the first and second-order phase transitions have been studied using the Monte Carlo simulations based on the heath bath algorithm. We have investigated the magnetic behavior of the system as a function of the temperature. The amplitude of the total susceptibility and the specific heat peaks increase by increasing the values of the magnetic field h. The magnetic entropy change Δ S m , the adiabatic temperature change Δ T a d are obtained for different external magnetic fields and temperatures. It is found that the system exhibits an inverse magnetocaloric effect when we have a ferrimagnetic interaction between the two sublattices. The relative cooling power (RCP) increases with increasing the external magnetic field and decreases with the temperature. The hysteresis loops of the system are examined as a function of the Hamiltonian parameters the result obtained show that the system may display various hysteresis behaviors such triple, double, single loop and step-like loops. [ABSTRACT FROM AUTHOR]

• The thermodynamic properties of anisotropy ferrimagnetic chain with bond alternation were studied. • At Heisenberg point, the energy gap between two branches is 1.7641, free energy is -1.4659 and ground-state energy is -0.7326. • The effect of anisotropy and bonding alternation on thermodynamic quantities are consistent with other establish methods. We investigate the finite temperature properties of anisotropic ferrimagnetic chain with bond alternation. The spin excitation spectrum as well as the thermodynamic quantities are calculated by means of the extended self-consistent mean-field theory. Two branches of energy spectrum are obtained and the energy gap between them is 1.7641 at zero temperature which agrees quite well with other numerical results. The contribution of bonding alternation δ , anisotropy λ and magnetic field H to the energy gap are present in this research. The other thermodynamic quantities varying with δ and λ , such as ground state energy e , free energy f , specific heat c m , magnetization m and uniform magnetic susceptibility T χ u n i / N g 2 are explicitly discussed, respectively. At Heisenberg point, the e 0 is -0.7326 and f 0 is -1.4659 at zero temperature in this work are reasonable compared with the results calculated by other methods. The effect of λ and δ on the thermodynamic quantities at finite temperature are also well consistent with other established methods. [ABSTRACT FROM AUTHOR]