Easy-plane Magnetocrystalline Anisotropy Research Articles

First-principles study on the p-orbital multiferroicity of single-layer XN (X = Ge, Sn, Pb)

Two-dimensional (2D) multiferroic materials have triggered a burst of interest owing to their wide applications in nanoelectronics. Specifically, p-orbital multiferroicity is strongly desired but has been very few reported. Here, based on first-principles calculations, we unveil a new type of 2D multiferroic material: the single-layer (SL) XN (X = Ge, Sn, Pb). Our findings show these materials are ferromagnetic semiconductors with strong magnetoelectric coupling and wide bandgaps. The multiferroicity is related to the unpaired p-orbital electrons of N atoms and the buckled crystal structure. All the single layers show easy-plane magnetocrystalline anisotropy, and the magnetic anisotropy energy increases significantly with the atomic number increasing. Our Monte Carlo simulations suggest the Curie temperature TC is 205.44 K, 200.45 K, and 287.88 K for SL GeN, SnN, and PbN, respectively. By applying tensile strain, the TC can be further increased to 225.39 K, 245.35 K, 369.99 K, respectively. Additionally, biaxial strain can induce semiconductor-to-half-metal and ferroelectricity-to-paraelectricity transition in the single layers. We aspire that our work contributes to the exploration of room-temperature p-orbital multiferroicity.

Large ordered moment with strong easy-plane anisotropy and vortex-domain pattern in the kagome ferromagnet Fe3Sn

We report the magnetic anisotropy of kagome bilayer ferromagnet Fe3Sn probed by the bulk magnetometry and magnetic force microscopy (MFM) on high-quality single crystals. The dependence of magnetization on the orientation of the external magnetic field reveals strong easy-plane magnetocrystalline anisotropy and anisotropy of the saturation magnetization. The leading magnetocrystalline anisotropy constant shows a monotonous increase from K1≈−1.0×106 J/m3 at 300 K to −1.3×106 J/m3 at 2 K. Our ab initio electronic structure calculations yield the value of total magnetic moment of 7.1 μB/f.u. and a magnetocrystalline anisotropy energy density of −0.57 meV/f.u. (−1.62×106J/m3) both being in reasonable agreement with the experimental values. The MFM imaging reveals micrometer-scale magnetic vortices with weakly pinned cores that vanish at the saturation field of ∼3 T applied perpendicular to the kagome plane. The observed vortex-domain structure is well reproduced by the micromagnetic simulations, using the experimentally determined value of the anisotropy and exchange stiffness.

Improvement of high-frequency magnetic properties in antiferromagnetic coupling trilayers by easy-plane magnetocrystalline anisotropy

Antiferromagnetic coupling ferromagnet/nonmagnet/ferromagnet structure trilayers with high resonance frequencies have been attracted much attention. However, their initial permeability is very low as the equivalent antiferromagnetic coupling field is an in-plane equivalent field. Therefore, how to improve the initial permeability and keep the high resonance frequencies is a worthy problem. In this work, an antiferromagnetic coupling Co82Ir18(35 nm)/Ru(0.35 nm)/Co82Ir18(35 nm) trilayer with easy-plane magnetocrystalline anisotropy was fabricated by direct current magnetron sputtering. The high-frequency magnetic properties and the tuning of optical mode ferromagnetic resonance in the trilayer were investigated using vector network analyzer with a shorted micro-strip method. The resonance frequency of the trilayer has a large increase (from 3.80 GHz to 8.16 GHz, the increment is 4.36 GHz) compared with the Co82Ir18(70 nm) single film due to the high-frequency optical mode resonance in the antiferromagnetic coupling ferromagnet/nonmagnet/ferromagnet structure. Moreover, through the introduction of easy-plane magnetocrystalline anisotropy, the calculated results reveal that initial permeability of our trilayer is the largest among other antiferromagnetic coupling Co-based trilayers without easy-plane magnetocrystalline anisotropy at the same resonance frequency (8.16 GHz), where the high-frequency magnetic properties of antiferromagnetic coupling trilayers are improved. Meanwhile, the tuning of optical mode ferromagnetic resonance reveals that the switch field about 161 Oe (about 1/2 of the single film) is observed which can switch the system from optical mode to acoustic mode. The results of this work indicate that it is effective to enhance the high-frequency magnetic properties of antiferromagnetic coupling trilayers by introducing the easy-plane magnetocrystalline anisotropy, which is a new method in improving the applied ability of antiferromagnetic coupling trilayers.

Temperature dependence of magnetic properties and ferromagnetic resonance in oriented hcp CoIr soft magnetic films with/without easy-plane magnetocrystalline anisotropy

The static magnetic properties and ferromagnetic resonance of the c-axis oriented hcp Co0.85Ir0.15 and Co0.98Ir0.02 soft magnetic films, with an easy-plane magnetocrystalline anisotropy (MA) and a c-axis MA, respectively, are investigated with temperature from 300 K down to 5 K. As the MA is opposite, opposite behavior in the temperature dependence of the effective demagnetization field Heff is observed: a decrement in Co0.98Ir0.02 film and an increment in Co0.85Ir0.15 film, respectively. Moreover, the resonance field HR(T) obtained under high frequency is different from that under low frequency for Co0.85Ir0.15 film, which is significantly different from the similar behavior in HR(T) under each frequency (6–18 GHz) for Co0.98Ir0.02 film. The fitting in HR(T) indicates that the opposite MA is also the primary reason for the different appearance in HR(T). Our findings provide supports to develop the advantages and applications of the soft magnetic films with easy-plane MA.

Magnetic order and crystalline electric field excitations of the quantum critical heavy-fermion ferromagnet CeRh6Ge4

CeRh$_6$Ge$_4$ is an unusual example of a stoichiometric heavy fermion ferromagnet, which can be cleanly tuned by hydrostatic pressure to a quantum critical point. In order to understand the origin of this anomalous behavior, we have characterized the magnetic ordering and crystalline electric field (CEF) scheme of this system. While magnetic Bragg peaks are not resolved in neutron powder diffraction, coherent oscillations are observed in zero-field $\mu$SR below $T_{\rm C}$, which are consistent with in-plane ferromagnetic ordering consisting of reduced Ce moments. From analyzing the magnetic susceptibility and inelastic neutron scattering, we propose a CEF-level scheme which accounts for the easy-plane magnetocrystalline anisotropy, where the low lying first excited CEF exhibits significantly stronger hybridization than the ground state. These results suggest that the orbital anisotropy of the ground state and low lying excited state doublets are important for realizing anisotropic electronic coupling between the $f$- and conduction electrons, which gives rise to the highly anisotropic hybridization observed in photoemission experiments.

Gyromagnetic ratio of oriented hcp Co1−x Ir x soft magnetic films

The gyromagnetic ratio γ is a key quantity that determines spin and magnetic properties. In this study, γ is investigated via the electric detection of ferromagnetic resonance and first-principles calculations for c-axis oriented hcp-Co1−x Ir x () soft magnetic films with easy-plane magnetocrystalline anisotropy. γ increases linearly from 19.13 GHz kOe−1 for pure Co film to 19.32 GHz kOe−1 at x= 0.23, which is in agreement with the calculated result. The calculations reveal that the primary reason for the variation of γ is the different trends in the spin and orbital magnetic moments of the neighboring Co atoms of Ir, especially the linear increase of the latter. An investigation into the electronic structure indicates that the increase in these orbital magnetic moments is due to the appearance of 3d unoccupied minority states moving towards the Fermi level, which is induced by the local lattice distortion centered at Ir. Our findings provide the important γ data for the applications of CoIr soft magnetic films in high-frequency electromagnetic and spintronic devices, and will provide guidance in the understanding of the dynamic magnetic properties in disordered binary magnetic alloys.

Magnetic and electronic properties of layered Sr2NiO2Cl2 with square planar coordination

Local coordination geometry is crucial in determining the physical properties of transition metal compounds. In this work, we report a detailed density functional theory study on the magnetic and electronic properties of layered Sr2NiO2Cl2, which possesses an unusual square planar coordination. Due to the crystal field and spin splitting, Ni 3d electrons fully occupy the dxz, dyz, and dxy orbitals, while partially occupy the dz2 and dx2-y2 states, leading to the high spin state of Ni2+ ions and strong antiferromagnetic in-plane nearest-neighbor exchange interaction J1. Thus, Sr2NiO2Cl2 is predicted to exhibit a G-type magnetic ground state, which all nearest-neighbor magnetic moments are antiparallel to each other in the NiO2 plane. A band gap is opened irrespective of the specific magnetic state since the unique square planar crystal field splitting. Finally, large orbital moments and giant easy-plane magnetocrystalline anisotropy energy are obtained, which is again related to the unique coordination environment.

First-principles study of the easy-plane magnetocrystalline anisotropy in bulk hcp Co1−xIrx

The soft magnetic material hcp CoIr has easy-plane magnetocrystalline anisotropy (MA) over a wide range of Ir content and has attracted interest from many researchers. This study presents a comprehensive investigation of the magnetization and MA of bulk hcp Co1−xIrx (0.03≤x≤0.25) alloys based on first-principles calculations. The results reveal that easy-plane MA is obtained for 0.06≤x<0.25, which agrees with the experimental results. The MA arises from the spin-orbit interactions of Co 3d orbitals. The Co1 atoms (the nearest neighbors of Ir atoms) and the Co2 atoms (the second nearest neighbors of Ir atoms) have different local environments; hence, the d orbitals split differently. Numerical calculations prove that the energy level alignment at the two sites plays an important role in determining the orientation of the local spin moments. The Co1 site preferentially adopts an in-plane local spin moment, while the Co2 site exhibits an out-of-plane local spin moment. The competition between the two sites determines the orientation of the easy axis of the hcp CoIr system. Our findings provide guidance for understanding and evaluating experimental studies on manipulating MA in disordered binary alloys.

Extended exchange interactions stabilize long-period magnetic structures in Cr1∕3NbS2

The topologically protected, chiral soliton lattice is a unique state of matter offering intriguing functionality, and it may serve as a robust platform for storing and transporting information in future spintronic devices. While the monoaxial chiral magnet Cr1∕3NbS2 is known to host this exotic state in an applied magnetic field, its detailed microscopic origin has remained a matter of debate. Here, we work towards addressing this open question by measuring the spin wave spectrum of Cr1∕3NbS2 over the entire Brillouin zone with inelastic neutron scattering. The well-defined spin wave modes allow us to determine the values of several microscopic interactions for this system. The experimental data are well-explained by a Heisenberg Hamiltonian with exchange constants up to the third nearest neighbor and an easy plane magnetocrystalline anisotropy term. Our work shows that both the second and third nearest neighbor exchange interactions contribute to the formation of the helimagnetic and chiral soliton lattice states in this robust three-dimensional magnet.

Domain Structure and Spin Reorientation in TbCo5 and DyCo5 Intermetallics

In this paper, we study the spin-reorientation processes in DyCo5 and TbCo5 intermetallic compounds by direct observation of domain structure (DS) realignment during the easy plane—easy cone—easy axis phase transitions. In addition to the analysis of DS changes due to temperature induced spin reorientation, a description is given of a newly discovered effect of surface out-of-plane domain reorientation produced by abrasion and/or indentation of the surface of macroscopic samples with overall easy-plane magnetocrystalline anisotropy.

Magnetic properties of Ni-Mn-Ga-Co-Cu tetragonal martensites exhibiting magnetic shape memory effect

Magnetic properties of Ni46Mn24Ga22Co4Cu4, (Ni45Mn23Ga22Co5Cu5, Ni46Mn22.5Ga23Co5Cu3.5) tetragonal martensites with c/a≈1.14 exhibiting near 10% magnetic field-induced strain (MFIS) were investigated between 10 and 500K and up to 9T field. The (001) easy plane magnetocrystalline anisotropy with K1(300K)=−1.95∙105J∙m−3 (K2<6%|K1|, K3<2%|K1|, MS(300K)=63Am2/kg) was about 30% lower than in the non-doped Ni50.5Mn30.4Ga19.1 reference, which can be related to a reduced c/a ratio in the doped material. In spite of different type of magnetocrystalline anisotropy compared to 10M martensite, the mechanism of MFIS is the same, i.e. with the typical first-quadrant magnetization hysteresis and {101} twin boundary motion.

Electronic and magnetic properties of 2H−NbS2 intercalated by 3d transition metals

The electronic structure and magnetic properties of the 2H-NbS$_2$ compound intercalated by Cr, Mn and Fe, have been investigated by means of the Korringa-Kohn-Rostoker (KKR) method. The calculations demonstrate easy plane magneto-crystalline anisotropy (MCA) of Cr$_{1/3}$NbS$_2$ monotonously decreasing towards the Curie temperature in line with the experimental results. The modification of the electronic structure results in a change of the easy axis from in-plane to out-of-plane. It is shown, that for Cr$_{1/3}$NbS$_2$ and Mn$_{1/3}$NbS$_2$ the in-plane MCA and Dzyaloshinskii-Moriya interactions results in a helimagnetic structure along the hexagonal $c$ axis, following the experimental observations. The negative exchange interactions in the Fe$_{1/3}$NbS$_2$ compound results in a non-collinear frustrated magnetic structure if the MCA is not taken into account. It is shown, however, that a strong MCA along the hexagonal $c$ axis leads to a magnetic ordering referred to as an ordering of the third kind, which was observed experimentally.

Tuning the magnetocrystalline anisotropy inRCoPOby means ofRsubstitution: A ferromagnetic resonance study

We report on broad-band electron spin resonance measurements performed within the itinerant ferromagnetic phase of $R$CoPO ($R$ = La, Pr, Nd and Sm). We reveal that the $R$ substitution is highly effective in gradually introducing a sizeable easy-plane magnetocrystalline anisotropy within the Co sublattice. We explain our results in terms of a subtle interplay of structural effects and of indirect interactions between the $f$ and $d$ orbitals from $R$ and Co, respectively.

Skyrmions in thin films with easy-plane magnetocrystalline anisotropy

We demonstrate that chiral skyrmionic magnetization configurations can be found as the minimum energy state in B20 thin film materials with easy-plane magnetocrystalline anisotropy with an applied magnetic field perpendicular to the film plane. Our observations contradict results from prior analytical work, but are compatible with recent experimental investigations. The size of the observed skyrmions increase with the easy-plane magnetocrystalline anisotropy. We use a full micromagnetic model including demagnetization and a three-dimensional geometry to find local energy minimum (metastable) magnetization configurations using numerical damped time integration. We explore the phase space of the system and start simulations from a variety of initial magnetization configurations to present a systematic overview of anisotropy and magnetic field parameters for which skyrmions are metastable and global energy minimum (stable) states.

Magnetic and structural characterization of nanosized BaCoxZn2−xFe16O27 hexaferrite in the vicinity of spin reorientation transition

Numerous applications of hexagonal ferrites are related to their easy axis or easy plane magnetocrystalline anisotropy configurations. Certain W-type ferrites undergo spin reorientation transitions (SRT) between different anisotropy states on magnetic field or temperature variation. The transition point can be tuned by modifying the chemical composition, which suggests a potential application of hexaferrites in room temperature magnetic refrigeration. Here we present the results of structural and magnetic characterization of BaCoxZn2−xFe16O27 (0.7 ≤ x ≤ 2) doped barium ferrites. Fine powders were prepared using a sol-gel citrate precursor method. Crystal structures and particle size distributions were examined by X-ray diffraction and transmission electron microscopy. The optimal synthesis temperature ensuring complete formation of single W-phase with limited grain growth has been determined. Spin reorientation transitions were revealed by thermomagnetic analysis and AC susceptibility measurements.

Easy-plane magnetocrystalline anisotropy in the multistep metamagnetCeIr3Si2

The magnetization $M(B)$, electrical resistivity $\ensuremath{\rho}$, and specific heat measurements are reported on a single-crystalline sample of $\mathrm{Ce}{\mathrm{Ir}}_{3}{\mathrm{Si}}_{2}$, whose structure is characterized with a zigzag chain of Ce ions along the orthorhombic $a$ axis. This compound undergoes magnetic transitions at 3.9 and $3.1\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. Easy-plane magnetocrystalline anisotropy is manifested in the magnetization process. For $B\ensuremath{\parallel}b$ and $B\ensuremath{\parallel}c$, $M(B)$ curves have a ferromagnetic component of $0.2--0.3\phantom{\rule{0.3em}{0ex}}{\ensuremath{\mu}}_{B}∕\mathrm{Ce}$ and show metamagnetic transitions in a field range from $0.7\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}1.3\phantom{\rule{0.3em}{0ex}}\mathrm{T}$. At $B=5\phantom{\rule{0.3em}{0ex}}\mathrm{T}$, $M(B\ensuremath{\parallel}b)$ and $M(B\ensuremath{\parallel}c)$ are 11 times larger than $M(B\ensuremath{\parallel}a)$. Electrical resistivity is also anisotropic, ${\ensuremath{\rho}}_{b}\ensuremath{\cong}{\ensuremath{\rho}}_{c}\ensuremath{\geqslant}2{\ensuremath{\rho}}_{a}$. The magnetic part of $\ensuremath{\rho}$ exhibits a double-peak structure with maxima at 15 and $350\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The analysis of $M(B)$ and paramagnetic susceptibility using a crystal-field model revealed unusually large energy splitting of 500 and $1600\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ for the two excited doublets, respectively. The overall splitting is comparable to the largest value ever reported for Ce compounds, $2000\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ in the unusual ferromagnet $\mathrm{Ce}{\mathrm{Rh}}_{3}{\mathrm{B}}_{2}$ with a closely related structure.

Complex magnetic behavior in single-crystalline CeRh 3Si 2

High-quality single crystal of a novel cerium silicide CeRh 3Si 2 was grown by the Czochralski pulling method in a tetra-arc furnace and studied by means of X-ray diffraction and magnetic measurements. The compound crystallizes with an orthorhombic structure of the CeRh 3Si 2-type. It orders antiferromagnetically at T N = 4.5 K and undergoes a subsequent antiferromagnetic phase transition just below T N . The magnetic behavior exhibits strong easy-plane magnetocrystalline anisotropy with the crystallographic a-axis being the hard magnetization direction. The magnetic ordering in CeRh 3Si 2 is very sensitive to applied magnetic field, what manifests itself in the occurrence of several successive metamagnetic transitions and a few field-dependent singularities in the magnetic susceptibility.

Structure and magnetic properties of Pr 1− δ(Co,Cu) 5+2 δ (0< δ

We have investigated the structure and magnetic properties of Pr 1− δ (Co,Cu) 5+2 δ (0< δ<0.22) compounds with the TbCu 7-type structure, using X-ray powder diffraction and magnetic measurements. The lattice parameters ( a and c) of Pr 1− δ (Co,Cu) 5+2 δ compounds increase with increasing Cu content since the radius of Cu is a little larger than that of Co. Our experimental results indicate that Cu may stabilize Pr 1− δ (Co,Cu) 5+2 δ compounds with the TbCu 7-type structure, but δ is only determined by the temperature. The X-ray patterns of magnetically aligned samples show that the compounds with x=2.0 and 3.0 exhibit easy-plane magnetocrystalline anisotropy. The saturation magnetization and Curie temperature decrease with increasing Cu content.

Magnetic properties of single crystalline UFeSi

A single crystal of UFeSi has been grown and studied with respect to crystal structure, magnetic and electrical resistivity behavior. UFeSi crystallizes in the orthorhombic TiNiSi-type crystal structure and shows no signs of magnetic ordering. The temperature dependence of magnetic susceptibility measured in all three principal crystallographic directions is weakly temperature-dependent, nevertheless it exhibits easy-plane magnetocrystalline anisotropy. The broad χ( T) maximum around 80 K observed in the a–c plane is reminiscent of spin-fluctuation behavior. The temperature dependence of electrical resistivity measured for a current along the b-axis obeys quadratic dependence for temperatures below 33 K and shows a tendency to saturation at high temperatures typical for most U intermetallics.

Theoretical calculation on the magnetocrystalline anisotropy of NdFe 10.5V 1.5N x

The NdFe 10.5V 1.5N x compounds with different nitrogen content have been synthesized. The dependence of magnetic properties at room temperature on the nitrogen content was investigated in order to give evidence of the importance of the nitrogen content on the magnetic anisotropy of the rare earth sublattice. In the meantime, the theoretical calculations were performed to analyze the nitrogen content dependence of the magnetocrystalline anisotropy constants K 1,2, as well as the anisotropy field H a in the NdFe 10.5V 1.5N x . The results confirmed that the second-order crystal-field parameter A 20 is dominant and, in the nitrides, the chief contribution to A 20 comes from nitrogen located at 2b sites. Finally, the increase of nitrogen content will first turn the easy-plane magnetocrystalline anisotropy of the rare earth sublattice into easy-axis one and then enhance it linearly to a much larger value, which is in quite good agreement with experiment.