FM State Research Articles

Surface and bulk characterization of magnetic multilayers formed within a single layer FeRh by hydrogen ion irradiation

In modern spintronics, magnetic multilayers, such as a ferromagnet/antiferromagnet (FM/AFM) heterostructure, are essential for achieving novel and practical capabilities, including the exchange bias effect, spin-transfer torque, tunneling magnetoresistance, etc. As these functions are determined by the exchange interaction or the carrier transport across the interface, it is critical to optimize the magnetic interface usually formed between different materials with the chemical mismatch as well as the structural discontinuity. Here, we explored the potential of FeRh for creating the FM/AFM multilayer within a single material by exploiting its tunability of the temperature-dependent AFM-FM transition with a hydrogen ion irradiation. We investigated bulk and surface magnetic states separately based on a magneto-optical Kerr effect and magnetization-induced second-harmonic generation, respectively, and could reveal that FeRh can host the FM (surface)/AFM (bulk) magnetic multilayer within a single layer of FeRh even at room temperature prepared with a hydrogen ion dose of 2.0×1015 H+/cm2. As the FM and AFM states are stabilized with a well-defined spatial separation as manifested by the exchange bias effect, we expect the FeRh-based FM/AFM bilayer to alleviate limitations arising from the interfaces formed by otherwise different materials.

Study of the magnetic and structural properties of the simple perovskite YFeO3

In the present work, an experimental and theoretical study of the synthesis, magnetic, and structural properties of simple perovskite compounds YFeO3 has been investigated based on their potential applications, such as: solid oxide fuel cells, electrochemical sensors, sensor materials, magneto-optical materials, etc. Experimentally, the synthesis was carried out by the sol-gel method. X-rays and Rietveld refinements confirmed the orthorhombic structure. Scanning electron microscopy observations confirmed agglomerates of simple perovskite particles YFeO3. The study of the magnetic phase of the simple perovskite YFeO3 showed that it behaves like a weak ferromagnetic, this property delimits and directs magnetic fields into well-defined trajectories. On the other hand, the structural results, from a theoretical point of view, are in good agreement with the experimental ones. Through energy comparison, a possible competition was identified between the FM and AFM states, where the electronic properties are associated with the directional nature of the hybridization between the p orbitals of oxygen and the t2g states, where the superexchange mechanism prevails with e oxygen as mediator.

Meron-Mediated Phase Transitions in Quasi-Two-Dimensional Chiral Magnets with Easy-Plane Anisotropy: Successive Transformation of the Hexagonal Skyrmion Lattice into the Square Lattice and into the Tilted FM State.

I revisit the well-known structural transition between hexagonal and square skyrmion lattices and subsequent first-order phase transition into the tilted ferromagnetic state as induced by the increasing easy-plane anisotropy in quasi-two-dimensional chiral magnets. I show that the hexagonal skyrmion order first transforms into a rhombic skyrmion lattice, which, adjusts into a perfect square arrangement of skyrmions ("a square meron-antimeron crystal") within a narrow range of anisotropy values. These transitions are mediated by merons and anti-merons emerging in the boundaries between skyrmion cells; energetically unfavorable anti-merons annihilate, whereas pairs of neighboring merons merge. The tilted ferromagnetic state sets in via mutual annihilation of oppositely charged merons; as an outcome, it contains bimeron clusters (chains) with the attracting inter-soliton potential. Additionally, I demonstrate that domain-wall merons are actively involved in the dynamic response of the square skyrmion lattices. As an example, I theoretically study spin-wave modes and their excitations by AC magnetic fields. Two found resonance peaks are the result of the complex dynamics of the domain-wall merons; whereas in the high-frequency mode the merons rotate counterclockwise, as one might expect, in the low-frequency mode merons are instead created and annihilated consistently with the rotational motion of the domain boundaries.

The magnetic properties, flat and Dirac bands of two-dimensional room-temperature ferromagnetic Kagome material Mn3Sn3Se2

The Kagome lattice is rich in unique electronic and magnetic properties, such as flat band, superconductivity, charge density waves, and so on. In this paper, the magnetic properties, flat and Dirac bands of monolayer Mn3Sn3Se2 with Kagome lattice are investigated based on first-principles calculations. A total of four magnetic configurations are considered, and the intrinsic ground state of Mn3Sn3Se2 is identified as the ferromagnetic state. Strain has a significant effect on its magnetic ground state, which changes to an in-plane AFM state when the tensile strain exceeds 5 %. Monolayer Mn3Sn3Se2 has an out-of-plane magnetic anisotropy of up to 0.777 meV, and the Curie temperature is 528 K. The band structure of the FM state is shown to be metallic, and spin polarized flat and Dirac bands appear near the Fermi level, which are degenerate. Monolayer Mn3Sn3Se2 changes to half-metallic when a strain of 1%–2% is applied. Strain and correlation effects can significantly alter the flatness of flat band and the relative energy with Dirac bands. These results not only enrich the family of two-dimensional ferromagnets, but also provide a reference for studying the regulation of flat and Dirac bands.

Ab initio calculations on magnetic and optical characteristics of pure ZnO and Mn(II)-doped ZnO monolayers with and without neutral charged vacancies defects

At high Curie temperatures, diluted magnetic semiconductors exhibit induced ferromagnetism and spin-dependent interactions, making them useful in magneto-electronic devices. In spite of the fact that ferromagnetism and optical emission dynamics are characterized by intricate microstructural and compositional features, the origins of these phenomena are not yet completely understood. Here, we used first principles calculations to study how vacancy defects affect the electrical, optical, and magnetic properties of pure ZnO and Mn@ZnO monolayers. In the pristine monolayer, the Zn vacancy produces magnetism with a total magnetic moment of 2 μB, but the oxygen vacancy does not. The magnetic semiconducting characteristic of the Mn substitution at the Zn site is shown by a total magnetization of 5 μB. The magnetic ground state of the ZnO monolayer doped with Mn is significantly influenced by the presence of native defects. More specifically, Zn vacancies are essential for stabilizing the FM states due to the bound magnetic polarons (BMPs) formation, but O vacancies have no influence on the magnetic ground state of the Mn(II)@ZnO monolayer. Based on the optical study, we discovered that Zn and O vacancies in the ZnO ML produce optical absorption peaks at 1.92 eV and 2.90 eV, respectively. The substitution of Mn(II) at Zn site not only increases the band gap of the ZnO monolayer but also produces d-d transition bands at lower energy side of fundamental energy gap peak. The Zn vacancies in the Mn(II)@ZnO ML produce an infrared absorption band around 1.13 eV, which could be due to the formation of the BMP, and enhance the optical absorption efficiency. The ZnO ML’s energy gap and Mn ion’s d-d transition bands exhibit a blueshift in AFM systems and a redshift in the FM systems. In far configuration, the Mn(II)@ZnO monolayer show no shift in the fundamental bandgap and intra-band transition of the Mn(II) spins due to the Mn(II) ion’s paramagnetic nature.

Mechanical, magnetic, and electronic characteristics of Sm-based chalcogenides for spintronics and device applications

To comprehend the mechanical, electronic, and magnetic properties of chalcogenides HgSm2S/Se4, a DFT-oriented thorough investigation is carried out. The elastic constants and spin-dependent electrical characteristics are determined by using the PBEsol-GGA functional and (mBJ) potential correspondingly. Through optimization, a sufficient amount of energy is discharged by the FM state as compared to nonmagnetic states. By investigating Born stability criteria and formation energy, the structural stabilities of both spinels are verified. The calculated Poisson's and Pugh's ratios showed that both spinels are ductile. The estimation of Curie temperature has supported the existence of a ferromagnetic nature at room temperature. Moreover, the presence of ferromagnetism in both spinels is confirmed by spin-oriented electrical characteristics, owing to the coupling between component states associated with Sm and S/Se.

Boosting the spin polarization and ferromagnetic stability of monolayer C3N through strategic mono-doping and co-doping with copper (Cu) and vanadium (V)

The impact of V and Cu doping on spin polarization and ferromagnetic stability in monolayer C3N was explored. Co-doping at 5.681 Å distances shows the strongest FM state, advancing spintronics applications.

Williamson-Hall technique for magnetic cooling in nanosized manganite LaNi0.25Mn0.75O3 and ferrite LaNi0.25Fe0.75O3

We addressed the physical characterisation and synthesis of both manganite LaNi0.25Mn0.75O3 (LNM) and ferrite LaNi0.25Fe0.75O3 (LNF) nanomaterials. Both samples were indexed to the orthorhombic structure with Pbnm (62) a space group. Scherrer method, Williamson-Hall technique, and Scanning Electron Microscopy (SEM) images prove that the materials are nano-sized. XPS measurements were investigated to study the structure of these materials. Magnetic data of the LNM system illustrate a Curie temperature at around TC = 221 K presenting a ferromagnetic to paramagnetic transition (FM/PM) while heating the sample. For the LNF sample, a blocking temperature TB = 250 K defining a transition from the superparamagnetism (SPM) to the blocked state of the ferromagnet/spin-glass (SG) order till attaining the irreversibility temperatures Tirr = 390 K where the FM state starts. It is demonstrated how both systems differ significantly via the relative cooling power (RCP) values confirming the important effect of the Mn compared to the Fe in magnetic refrigeration. The RCP (1 T) = 44.107 J/kg and RCP (7 T) = 374.257 J/kg for the LNM sample vs. RCP (1 T) = 1.047 J/kg and RC (7 T) = 19.543 J/kg for the LNF compound. The evolution rate at 7 T is around 1815% making the difference very clear and presenting the LNM system as a very suitable magnetic refrigerant.

Influence of high pressure on the remarkable itinerant electron behavior in Y0.7Er0.3Fe2D4.2 compound

A monoclinic Y0.7Er0.3Fe2D4.2 compound exhibits unusual magnetic properties with different field induced magnetic transitions. The deuteride is ferrimagnetic at low temperature, and the Er and Fe sublattices present magnetic transitions at different temperatures. The Er moments are ordered below TEr = 55 K, whereas the Fe moments remain ferromagnetically coupled up to TM0 = 66 K. At TM0, the Fe moments display a sharp ferromagnetic–antiferromagnetic transition (FM–AFM) through itinerant electron metamagnetic behavior very sensitive to any volume change. Y0.7Er0.3Fe2D4.2 becomes paramagnetic above TN = 125 K. The pressure dependence of TEr and TM0 has been extracted from magnetic measurements under hydrostatic pressure up to 0.49 GPa. Both temperatures decrease linearly upon applied pressure with dTEr/dP = −126 and dTM0/dP = −140 K GPa−1 for a field of B = 0.03 T. Both magnetic Er and ferromagnetic Fe orders disappear at P = 0.44(4) GPa. However, under a larger applied field B = 5 T, dTM0/dP = −156 K GPa−1, whereas dTEr/dP = −134 K GPa−1 showing weaker sensitivity to pressure and magnetic field. At 2 K, the decrease of the saturation magnetization under pressure can be attributed to a reduction of the mean Er moment due to canting and/or a crystal field effect. Above TM0, the magnetization curves display metamagnetic behavior from an AFM to FM state, which is also very sensitive to the applied pressure. The transition field Btrans, which increases linearly upon heating, is shifted to a lower temperature upon applied pressure with ΔT = −17 K between 0 and 0.11 GPa. These results show strong decoupling of the Er and Fe magnetic sublattices vs temperature, applied field, and pressure.

Strong magnetic anisotropy in PrRu2Ga8 and PrCo2Al8 single crystals

Single crystals of LnRu2Ga8 and LnCo2Al8 (Ln = La and Pr) were grown using a Ga/Al self-flux method. An orthorhombic CaCo2Al8-type structure with space group Pbam (No.55) of them was identified by x-ray diffraction. LaRu2Ga8 and LaCo2Al8 are Pauli paramagnetic down to 2 K, while PrRu2Ga8 and PrCo2Al8 show antiferromagnetic (AFM) order at 2.5 and 5 K, respectively. Strong magnetic anisotropy in PrRu2Ga8 and PrCo2Al8 single crystals was found by an anisotropic magnetic measurement. The field-induced FM state was observed in both PrRu2Ga8 and PrCo2Al8 for H||c. However, in the case of H⊥c, the AFM state is robust. The strong magnetic anisotropy in PrRu2Ga8 FM and PrCo2Al8 is due to their anisotropic magnetic interactions that FM interactions are dominant in the case of H||c while AFM interactions for H⊥c.

Control of coexistent phase by rotation of magnetic field in a metamagnetic FeRh thin film

Here, we report the change of the FM and AF coexistent state in a MPTM FeRh thin film by simply rotating of the magnetic field. We find that the resistance of the coexistent phase can be changed by up to 19% by the rotation of the magnetic field. This kind of resistance change is obviously different from the usual anisotropic magnetoresistance in metallic materials whether in the angle-dependent behavior or in the magnitude. These results show another way to control the FM-AF coexistent phase, which determines the multifunctional properties of the MPTMs.

Two states of magnetic frustration in La0.7Sr0.3MnO3 amorphous films with fractal structures: New knowledge about clusters and cluster ensembles

In amorphous La0.7Sr0.3MnO3 films with a fractal structure, two states of magnetic frustration were found, which are the characteristic of cluster spin glass (CSG) and spin glass (SG) states and are associated with the presence of competing, FM and AFM, magnetic interactions, and the geometry of fractal formations. A high density of clusters in them provides effective magnetic interactions of magnetic moments without the participation of free charge carriers. It has been established that the formation of CSG begins with the transition of the central parts of the clusters to the FM state (at T < 98 K) and ends with the formation of the AFM order in the peripheral areas of the clusters, at T < 64 K. Increasing the field to H = 1.2 kOe, which stimulates AFM ordering of peripheral areas, strengthens the state of the cluster glass. A further decrease in temperature (T < 26 ) and an increase in the field (H > 2.5 kOe) causes the transition of peripheral areas from the AFM to the SG state. A phenomenological description of the frustration process is made. The dependences of the order parameter and barrier height on temperature and magnetic field have been studied. The consequences of the CSG ⇒ SG phase transition for the magnetism of the samples and the direct influence of the external field on their magnetic structure are discussed.

First principles investigation on half metallic ferromagnetism properties of cubic VLaO3 compound

In this investigation, we thoroughly examined the equilibrium structural, electrical, magnetic, elastic, thermodynamic, as well as thermoelectric behavior of the vanadium lanthanum oxide perovskite VLaO3. The computations were executed with the FP-LAPW method, as in cooperated in the WIEN2k package that rely on the first principles method, using generalized gradient approximation (PBE-GGA). The explored compound has been observed to be ferromagnetically stable i.e., in FM phase as it has lowest energy in FM state than in paramagnetic phase i.e., in NM phase. The thermodynamical and mechanical stability of the studied VLaO3 compound is also assured by evaluating its formation energy, cohesive energy and second order elastic constants. Furthermore, our computed findings reveal that the studied compound belongs to half metallic perovskites with an energy gap of 2.56 eV in the majority spin and possesses a total magnetic moment of 3.99µB/unit cell. Additionally, the thermal as well as pressure dependence of volume, specific heat capacity, and bulk modulus are also examined with the aid of GIBBS which rely on quasi harmonic Debye theory. Finally, the thermoelectric transport properties are also evaluated as a function of chemical potential in the range extending from −2.0 eV to 2.0 eV for different temperatures at 300 K, 700 K and 1200 K to explore budding possibility of this compound for energy harvesting applications.

Correlation of the crystal features, magnetic parameters, and electronic structure of Bi-substituted BaFe12-xBixO19 hexaferrites: Theoretical background

Herein, using first-principles density functional theory (DFT) calculations, we have investigated the effects of Bi substitution on the structural, electronic, and magnetic properties of barium hexaferrite (BaFe12-xBixO19, x = 0; 0.5; 1.5 and 2). As a result of the calculation, it was determined that the most stable structure exists if the spin of the Fe atom on the 2a, 2b, and 12k positions of the barium hexaferrite compound is taken in the upward direction. The calculated lattice constant ca=3.9 and magnetic moment (4.24μB) of iron ions are in reasonable agreement with other experimental works. Moreover, the presence of bismuth reduces the electronic band gap. Energy gain and magnetic anisotropy energy calculations for FIM, FM, and NM states were performed for the most stable states. It has been established that the most stable structural state is characteristic of х = 0.5. It has been calculated that substitution by the large Bi3+ ion dramatically changed the electronic structure and sharply reduced the band gap. This paper is the first step towards establishing the nature of the distribution of ions in M-type hexaferrites under conditions of substitution by ions with a large ionic radius.

Computational study of electronic, magnetic, and optical properties of Fe(II) mono-doped and (Fe(II), Al) co-doped ZnTe

Future information technology will rely mainly on spin-related optical properties; however, these properties require microscopic anti-ferromagnetic coupling, ferromagnetic coupling between d-states, or magnetic interaction between transition metal ions and excitons, all of which are poorly understood in these diluted magnetic semiconductors (DMS). In the present work, we performed first-principles calculations to study the magnetic, opto-electronic properties of Fe(II)-doped ZnTe. The results show that Fe(II) doping at the Zn site changes the ground state of ZnTe from non-magnetic to magnetic, with total magnetization of 4 μB. The observed competing ferro- and anti-ferromagnetism in Fe(II)-doped ZnTe can be described on the basis of the RKKY-exchange process. However, the electron introduced by Al co-doping can change the most stable configuration C-1 from AFM to FM state and an estimated curie temperature above room temperature is obtained. The optical properties of pure ZnTe and doped samples have been calculated, and we find that the bandgap (2.14 eV) of ZnTe is shifted to a lower energy with the increase in Fe(II) doping. The spin-allowed d-d transition of Fe ion in the tetrahedral crystal field is observed in the infra-red region of light. Furthermore, the correlation of magnetic coupling of Fe-ions with optical bandgap energy and d-d intra-band transition bands of Fe(II) has been investigated, and we find that the optical bandgap and spin-allowed d-d transition are blue shifted (red-shifted) in AFM (FM) coupled Fe-ion systems, supporting the experimental observations. The improved opto-electronic and magnetic properties of Fe(II)-doped ZnTe by n-type (Al) co-doping provide insight into the potential applications of these materials in spin-related photonic and spintronic devices such as photovoltaics and remote sensing.

Comparative examination of the physical parameters of the sol gel produced compounds La0.5Ag0.1Ca0.4MnO3 and La0.6Ca0.3Ag0.1MnO3

In this paper, the physical characteristics of La0.5Ag0.1Ca0.4MnO3 and La0.6Ca0.3Ag0.1MnO3 compounds have been studied. Structural analysis by XRD showed that both samples crystallize in an orthorhombic structure. For the La0.5Ag0.1Ca0.4MnO3 sample it can be seen that there are two bands: the first is due to the stretching Mn–O bond the \({\upsilon }_{s}\) vibration mode, relates to the internal motion of a length-changing Mn–O, whereas the second corresponds to the \({\upsilon }_{b}\) bonding mode, which is sensitive to a change in the Mn–O–Mn angle. For the compound La0.6Ca0.3Ag0.1MnO3 the \({\upsilon }_{b}\) band is absent. The magnetic measurements show that the two compounds have a single transition from the PM state to the FM state with an increase in the Curie transition temperature \({T}_{c}\) for the compound La0.6Ca0.3Ag0.1MnO3. Similarly, the substitution of silver in calcium increases the value of the magnetization at low temperature. We also studied the magnetocaloric effect of our compounds. This study shows a significant change in magnetic entropy \(\Delta {S}_{M}\) that took place around their magnetic transition temperatures \({T}_{c}\). Under the influence of a 5 T magnetic field. The largest fluctuation in magnetic entropy is in the order of − 8.67 J/kg·K for the compound La0.6Ca0.3Ag0.1MnO3 this value is considered significant. The magnetocaloric results indicate that the compound La0.6Ca0.3Ag0.1MnO3 is the best sample which has a large RCP which suggests its good candidate in the field of magnetic cold. Based on the Banarjee criterion and Landau theory, a second-order transition is observed for both samples in the vicinity of the Curie transition \({T}_{c}\). The experimentally obtained value of \({\Delta S}_{M}\) is smaller than the theoretically calculated one, which proves that the transition is an unconventional transition even under the influence of a 5 T magnetic field.

Computational insights into electronic, magnetic and optical properties of Mn(II)-doped ZnTe with and without vacancy defects

First principles calculations have been performed to investigate the optoelectronic and magnetic properties of Mn(II); ZnTe DMS with and without native defects using first principle calculations. Our results find that anti-ferromagnetic coupling dominates in the pure Mn(II)-doped ZnTe system due to super-exchange (SE) mechanism. The impact of p-type and n-type defects on magnetic coupling in Mn(II)-doped ZnTe were discussed and we found that p-type defect such as Zn vacancy defects play important role in stabilization of FM state due to the formation of bound magnetic polaron (BMP) while n-type defect such as Te vacancy defect does not affect the ground state of Mn(II); ZnTe. The magnetic coupling of Mn(II) spins in the absence and presence of Zn vacancy were explained on the basis of phenomenological band structure model. The optical absorption spectra of pure ZnTe and Mn(II); ZnTe with and without vacancies have been investigated and we found that single Mn(II)-doping in the lattice of ZnTe generates an absorption band at energy around 2.02 eV, which is assigned to intra-band d-d transitions of Mn(II) dopant. The band at energy around 0.44 eV in the absorption spectrum of Mn(II)-doped ZnTe with Zn-vacancy may be due to the acceptor states produced by Zn vacancy at Fermi level and band around 1.6 eV in the spectrum of Te vacancy defect system are related to the donor states produced by Te vacancy defect. Moreover, the correlation of magnetic coupling with intra-band d-d transition bands and fundamental bandgaps of ZnTe were also discussed and it was found that intra-band transition peak of Mn(II) ions and optical band gap of ZnTe are blue-shift in AFM coupled Mn(II) ions and are red-shift in FM coupled ions system. Our present findings highlight the worthwhile half-metallic properties of Mn(II)-doped ZnTe, which can be obtained via Zn vacancy defect engineering; this can find broad applications for the fabrication of optoelectronic and spintronic devices.

Exchange interactions in d5 Kitaev materials: From Na2IrO3 to α−RuCl3

We present an analytical study of the exchange interactions between pseudospin one-half ${d}^{5}$ ions in honeycomb lattices with edge-shared octahedra. Various exchange channels involving Hubbard $U$, charge-transfer excitations, and cyclic exchange are considered. Hoppings within ${t}_{2g}$ orbitals as well as between ${t}_{2g}$ and ${e}_{g}$ orbitals are included. Special attention is paid to the trigonal crystal field $\mathrm{\ensuremath{\Delta}}$ effects on the exchange parameters. The obtained exchange Hamiltonian is dominated by ferromagnetic Kitaev interaction $K$ within a wide range of $\mathrm{\ensuremath{\Delta}}$. It is found that a parameter region close to the charge-transfer insulator regime and with a small $\mathrm{\ensuremath{\Delta}}$ is most promising to realize the Kitaev spin liquid phase. Two representative honeycomb materials ${\mathrm{Na}}_{2}{\mathrm{IrO}}_{3}$ and $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{RuCl}}_{3}$ are discussed based on our theory. We have found that both materials share dominant ferromagnetic $K$ and positive nondiagonal $\mathrm{\ensuremath{\Gamma}}$ values. However, their Heisenberg $J$ terms have opposite signs: AFM $J>0$ in ${\mathrm{Na}}_{2}{\mathrm{IrO}}_{3}$ and FM $J<0$ in $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{RuCl}}_{3}$. This brings different magnetic fluctuations and results in their different magnetization behaviors and spin excitation spectra. Proximity to FM state due to the large FM $J$ is emphasized in $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{RuCl}}_{3}$. The differences between the exchange couplings of these two materials originate from the opposite $\mathrm{\ensuremath{\Delta}}$ values, indicating that the crystal field can serve as an efficient control parameter to tune the magnetic properties of ${d}^{5}$ spin-orbit Mott insulators.

Robust electronic and tunable magnetic states in Sm2 NiMnO6 ferromagnetic insulator

Ferromagnetic insulators (FM-Is) are the materials of interest for the new generation quantum electronic applications. Here, we have investigated the physical observables depicting FM-I ground states in epitaxial Sm2NiMnO6 (SNMO) double perovskite thin films fabricated under different conditions to realize the different level of Ni/Mn anti-site disorders (ASDs). The presence of ASDs immensely influence the characteristic magnetic and anisotropy behaviors in SNMO system by introducing short scale antiferromagnetic interactions in predominant long range FM ordered host matrix. Charge disproportion between cation sites, in the form of Ni2+ + Mn4+ → Ni3+ + Mn3+, causes mixed valency in both Ni and Mn species, which is found insensitive to ASD concentrations. Temperature dependent photo emission, photo absorption measurements duly combined with cluster model configuration interaction simulations, suggest that the eigenstates of Ni and Mn cations can be satisfactorily described as a linear combination of the unscreened d n and screened (: O 2p hole) states. The electronic structure across the Fermi level (E F) exhibits closely spaced Ni 3d, Mn 3d and O 2p states. From occupied and unoccupied bands, estimated values of the Coulomb repulsion energy (U) and ligand to metal charge transfer energy (Δ), indicate charge transfer insulating nature, where remarkable modification in Ni/Mn 3d—O 2p hybridization takes place across the FM transition temperature. Existence of ASD broadens the Ni, Mn 3d spectral features, whereas the spectral positions are found to be unaltered. Hereby, present work demonstrates SNMO thin film as a FM-I system, where the FM state can be tuned by manipulating ASD in the crystal structure, while the I state remains intact.

Study of half metallic ferromagnetism and thermoelectric properties of spinel chalcogenides BaCr2X4 (X = S, Se, Te) for spintronic and energy harvesting

The control of spin degree of freedom in electronics open new horizons to manipulate, transfer, and storage data at fasters speed. For this the structural, electronic, and magnetic characteristics of BaCr2X4 (X = S, Se, Te) spinels are addressed comprehensively. The more energy release in ferromagnetic states than antiferromagnetic states, and formation energy verified thermal stability in FM states. The Curie temperature, and spin polarization density have been reported for room temperature ferromagnetism. The detail and nature of ferromagnetism have illustrated by band structures, density of states, hybridization, double exchange mechanism, crystal field energy, exchange energies and exchange constants. The transfer of magnetic moment from Cr sites to other nonmagnetic sites (Ba, X) ensures the ferromagnetism due to exchange of electrons instead of clustering. Moreover, thermoelectric characteristics are explored with spin (↑) and spin (↓) separately in terms of conductivities, Seebeck coefficient, and power factor. Finally combined the spins to analyze the thermoelectric importance for real applications.