MAGNETIZATION AND INHOMOGENEOUS MAGNETOELECTRIC EFFECT IN A NANO-SIZED TWO-LAYER FERROMAGNETIC FILM WITH A COMBINED UNIAXIAL AND CUBIC ANISOTROPY IN LAYERS

2021 ◽  
Vol 0 (1) ◽  
pp. 23-26
Author(s):  
N.V. SHULGA ◽  
◽  
R.A. DOROSHENKO ◽  
Keyword(s):  
Ground State ◽  
Easy Axis ◽  
Magnetoelectric Effect ◽  
Numerical Study ◽  
Uniaxial Anisotropy ◽  
Polarization Vector ◽  
Ferromagnetic Film ◽  
Electric Polarization ◽  
Ferromagnetic Plate ◽  
Cubic Anisotropy

A numerical study of the magnetization reversal of a two-layer exchange-coupled ferromagnetic plate of finite dimensions, which has a combined uniaxial anisotropy (of the "easy axis" type for the upper layer and «easy plane» for the lower one) and cubic anisotropy with orientation [111]. It is shown that, in the presence of cubic anisotropy, the ground state of magnetization turns out to be uniform in the plane of the film. However, there is discontinuity at the interface between the film layers. This inhomogeneity can lead to the appearance of electric polarization due to the magnetoelectric effect. The electric polarization vector in this case lies in the plane of the film. Its modulus increases with increasing cubic anisotropy. In addition, with an increase in cubic anisotropy, a hysteresis of electrical polarization is observed.

The Magnetoelectric Effect in Ferroelectric/Ferromagnetic Film Hybrid Systems with Easy-Plane and Easy-Axis Anisotropy

2020 ◽  
Vol 65 (11) ◽  
pp. 1832-1836
Author(s):  
N. S. Gusev ◽  
M. V. Sapozhnikov ◽  
O. G. Udalov ◽  
I. Yu. Pashen’kin ◽  
P. A. Yunin
Keyword(s):  
Hybrid Systems ◽  
Easy Axis ◽  
Magnetoelectric Effect ◽  
Ferromagnetic Film ◽  
Easy Plane

scholarly journals Large linear magnetoelectric effect and field-induced ferromagnetism and ferroelectricity in DyCrO4

2019 ◽  
Vol 11 (1) ◽  
Author(s):  
Xudong Shen ◽  
Long Zhou ◽  
Yisheng Chai ◽  
Yan Wu ◽  
Zhehong Liu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Spin Structure ◽  
Magnetoelectric Effect ◽  
Electric Polarization ◽  
Metamagnetic Transition ◽  
Ferromagnetic Component ◽  
Antiferromagnetic Structure ◽  
Field Control ◽  
Ferromagnetic Magnetization

Abstract All the magnetoelectric properties of scheelite-type DyCrO4 are characterized by temperature- and field-dependent magnetization, specific heat, permittivity, electric polarization, and neutron diffraction measurements. Upon application of a magnetic field within ±3 T, the nonpolar collinear antiferromagnetic structure leads to a large linear magnetoelectric effect with a considerable coupling coefficient. An applied electric field can induce the converse linear magnetoelectric effect, realizing magnetic field control of ferroelectricity and electric field control of magnetism. Furthermore, a higher magnetic field (>3 T) can cause a metamagnetic transition from the initially collinear antiferromagnetic structure to a canted structure, generating a large ferromagnetic magnetization up to 7.0 μB f.u.−1. Moreover, the new spin structure can break the space inversion symmetry, yielding ferroelectric polarization, which leads to coupling of ferromagnetism and ferroelectricity with a large ferromagnetic component.

scholarly journals Dimer description of the SU(4) antiferromagnet on the triangular lattice

2020 ◽  
Vol 8 (5) ◽  
Author(s):  
Anna Keselman ◽  
Lucile Savary ◽  
Leon Balents
Keyword(s):  
Phase Diagram ◽  
Triangular Lattice ◽  
Ground State ◽  
Degrees Of Freedom ◽  
Numerical Study ◽  
Spin Model ◽  
Translation Invariance ◽  
Multilayer Graphene ◽  
High Symmetry ◽  
Starting Point

In systems with many local degrees of freedom, high-symmetry points in the phase diagram can provide an important starting point for the investigation of their properties throughout the phase diagram. In systems with both spin and orbital (or valley) degrees of freedom such a starting point gives rise to SU(4)-symmetric models. Here we consider SU(4)-symmetric "spin'' models, corresponding to Mott phases at half-filling, i.e. the six-dimensional representation of SU(4). This may be relevant to twisted multilayer graphene. In particular, we study the SU(4) antiferromagnetic "Heisenberg'' model on the triangular lattice, both in the classical limit and in the quantum regime. Carrying out a numerical study using the density matrix renormalization group (DMRG), we argue that the ground state is non-magnetic. We then derive a dimer expansion of the SU(4) spin model. An exact diagonalization (ED) study of the effective dimer model suggests that the ground state breaks translation invariance, forming a valence bond solid (VBS) with a 12-site unit cell. Finally, we consider the effect of SU(4)-symmetry breaking interactions due to Hund's coupling, and argue for a possible phase transition between a VBS and a magnetically ordered state.

scholarly journals Dynamics of Magnetization in Multilayer TbCo / FeCo Structures under the Influence of Femtosecond Optical Excitation

2019 ◽  
Vol 7 (3) ◽  
pp. 50-58 ◽  
Author(s):  
N. A. Ilyin ◽  
A. A. Klimov ◽  
N. Tiercelin ◽  
P. Pernod ◽  
E. D. Mishina ◽  
...  
Keyword(s):  
Easy Axis ◽  
Uniaxial Anisotropy ◽  
Anisotropy Field ◽  
Optical Excitation ◽  
Spin Precession ◽  
Heat Diffusion ◽  
Easy Magnetization ◽  
Test Beam ◽  
Magnetic Subsystem ◽  
Hard Axis

The need to study ultrafast processes in magnetism is due to the prospects for creating ultrafast magnetic recording and ultrafast spintronic devices. In order to excite the magnetic subsystem femtosecond optical pulses are used. The excitement is manifested as in spin precession. In metals, the material is heated first due to significant optical absorption, and significant Joule losses occur. The most important task is to search for materials in which spin processes are excited without heating. Obvious candidates are weakly absorbing materials, such as ferrite garnets. However, the range of such materials and the range of their functionality are limited.The purpose of this work is to study the dynamics of systems with nonthermal mechanisms of spin precession excitation. Such excitation is possible in ferromagnetic / antiferromagnetic heterostructures with exchange interaction, provided that the recombination time of photocarriers is shorter than the time of heat diffusion. Multilayer TbCo / FeCo structures of the near IR range were investigated for a femtosecond optical pulse. The spin dynamics are compared with the direction of the wave vector of the exciting pulse along and perpendicular to the axis of easy magnetization of the structures (“easy axis” and “hard axis” geometry, respectively). It is shown that in case of “easy axis” geometry the determinative mechanism is the thermal interaction. When the system is exposed to an excitation pulse, this mechanism leads to a decrease in the projection of magnetization on the direction of propagation of the test beam. In case of “hard axis” geometry, the magnetization turns to the magnetic field at the initial stage. Then it precesses and relaxes to an equilibrium angular orientation. Such dynamics indicate a rapid recovery of the uniaxial anisotropy field after laser irradiation. The presented results demonstrate an ultrafast change in the magnetic anisotropy induced during the fabrication of the heterostructure under study, which may be of interest for optical control of the orientation of the magnetization.

scholarly journals Pressure Effects on the Magnetic Phase Diagram of the CeNMSb2 (NM: Au and Ag): A DFT Study

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2237
Author(s):  
Mowafaq Mohammad Alsardia ◽  
Jaekyung Jang ◽  
Joo Yull Rhee
Keyword(s):  
Ground State ◽  
Noble Metals ◽  
Easy Axis ◽  
Magnetic Phase ◽  
Magnetic Phase Diagram ◽  
Pressure Effects ◽  
Spin Orbit ◽  
Magnetic Ground State ◽  
Magnetic Easy Axis ◽  
Spin Orbit Interactions

We explore the influence of pressure on the magnetic ground state of the heavy-fermion antiferromagnet (ferromagnet) CeAuSb 2 (CeAgSb 2 ) using first-principles calculations. The total-energy differences obtained by including the spin-orbit interactions and the on-site Coulomb potential for the Ce-derived 4f-orbitals are necessary to realize the accurate magnetic ground state of CeNMSb 2 (NM: Au and Ag). According to our results, the appearance of a new magnetic phase of CeAuSb 2 (CeAgSb 2 ) at the pressure of 2.1 GPa (3.5 GPa) is due to the rotation of the magnetic easy axis from the <001> to the <100> direction. Additionally, our data confirm that CeAgSb 2 is antiferromagnetic (AFM) above a critical pressure P c , and such a tendency is expected for CeAuSb 2 and remains to be seen. Through the spin-orbit-coupling Hamiltonian and detailed information on the occupation of individual 4f-orbitals of the Ce atom obtained by the electronic-structure calculations, we can deduce the rotation of the magnetic easy axis upon the application of pressure. According to the present and previous studies, the differences among the magnetic properties of CeNMSb 2 (NM: Cu, Ag and Au) compounds are not due to the different noble metals, but due to the subtle differences in the relative position of Ce atoms and, in turn, different occupations of Ce 4f-orbitals.

scholarly journals Microstructures and Soft Magnetic Properties of High Saturation Magnetization Fe-Co-N alloy Thin Films

2000 ◽  
Vol 614 ◽  
Author(s):  
N. X. Sun ◽  
S. X. Wang ◽  
Chin-Ya Hung ◽  
Chester X. Chien ◽  
Hua-Ching Tong
Keyword(s):  
Saturation Magnetization ◽  
Easy Axis ◽  
Uniaxial Anisotropy ◽  
Single Layer ◽  
Soft Magnetic Materials ◽  
High Saturation Magnetization ◽  
Soft Magnetic ◽  
Hard Axis ◽  
High Saturation ◽  
Significant Difference

ABSTRACTHigh saturation magnetization soft magnetic materials are required for future high-density recording heads as well as high frequency inductors. In this work, (Fe0.7Co0.3)1−xNx (or in short FeCoN) alloy films were synthesized with a high saturation magnetization of 24.5 kG, a hard axis coercivity of 5 Oe, an easy axis coercivity of 18 Oe, and a resistivity of 55 μΩcm. The FeCoN film sandwiched between two permalloy layers (5 nm) shows very good magnetic softness, a low hard axis coercivity of 0.6 Oe, an easy axis coercivity of 7.8 Oe, an excellent in-plane uniaxial anisotropy with an anisotropy of about 20 Oe, an initial permeability of 1000, and a roll-off frequency of 1.5 GHz. In order to understand the effect of the permalloy layers on the FeCoN layer, we fabricated four film structures: single layer FeCoN film; FeCoN film sandwiched between two permalloy layers on both sides; FeCoN film with one permalloy layer as the underlayer; and FeCoN film with one permalloy layer as caplayer. All these film structures were both magnetically and structurally characterized and compared. Structural characterization shows that there is no significant difference in the grain size of the FeCoN single layer and the FeCoN layer sandwiched between two permalloy layers. The four film structures have almost the same amount of compressive stress, about −300 MPa; and their saturation magnetostriction constants are also very close, in the range of 39.6×10−6 to 44.3×10−6. Difference in the crystallographic textures was observed in the pole figures for the FeCoN single layer and FeCoN film with permalloy underlayer.

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