Nonmagnetic Interlayer Research Articles

Random single-ion anisotropy in an Ising bilayer film with non-magnetic inter-layers

The magnetic properties (phase diagrams and magnetizations) of an Ising bilayer film with non-magnetic inter-layers are investigated by the use of the effective field theory with correlations. The system is consisted of two magnetic layers where upper and lower layers are respectively consisted from spin-1/2 atoms and spin-1 atoms with a single-ion anisotropy Di. The value of Di is randomly distributed by a bimodal distribution function. The possibility of multi-compensation points and the reentrant phenomena are obtained.

Phase Transition in a Spin-1/2 and Spin-1 Ising Bilayer Film with Non-magnetic Inter-layers

The phase transition, phase diagrams, and magnetizations of an Ising bilayer film with non-magnetic inter-layers are investigated by the use of the effective field theory with correlations. The system is consisted of two magnetic layers where upper and lower layers are consisted of spin-1/2 atoms and spin-1 atoms with a single-ion anisotropy. It is examined how the system may exhibit the tricritical behavior and some characteristic features of ferrimagnetism. The effects of non-magnetic layers on the magnetic properties are clarified.

Ferrimagnetism in an Ising Bilayer Film with a Transverse Field and Nonmagnetic Interlayers

The phase diagram and total magnetization of an Ising bilayer film with nonmagnetic interlayers are investigated by the use of the effective field theory with correlations. The system is consisted of two spin-1/2 magnetic layers where one of them is canted from the easy-axis (or z-) direction due to an applied transverse field, and they are coupled by an indirect exchange interaction. It is examined whether the system may exhibit some characteristic features of ferrimagnetism, such as a compensation point. The effects of nonmagnetic layers on them are clarified.

Calibration of multi-layered probes with low/high magnetic moments

We present a comprehensive method for visualisation and quantification of the magnetic stray field of magnetic force microscopy (MFM) probes, applied to the particular case of custom-made multi-layered probes with controllable high/low magnetic moment states. The probes consist of two decoupled magnetic layers separated by a non-magnetic interlayer, which results in four stable magnetic states: ±ferromagnetic (FM) and ±antiferromagnetic (A-FM). Direct visualisation of the stray field surrounding the probe apex using electron holography convincingly demonstrates a striking difference in the spatial distribution and strength of the magnetic flux in FM and A-FM states. In situ MFM studies of reference samples are used to determine the probe switching fields and spatial resolution. Furthermore, quantitative values of the probe magnetic moments are obtained by determining their real space tip transfer function (RSTTF). We also map the local Hall voltage in graphene Hall nanosensors induced by the probes in different states. The measured transport properties of nanosensors and RSTTF outcomes are introduced as an input in a numerical model of Hall devices to verify the probe magnetic moments. The modelling results fully match the experimental measurements, outlining an all-inclusive method for the calibration of complex magnetic probes with a controllable low/high magnetic moment.

Spin-current-induced magnetoresistance in trilayer structure with nonmagnetic metallic interlayer

We have theoretically investigated the spin Hall magnetoresistance (SMR) and Rashba–Edelstein magnetoresistance (REMR), mediated by spin currents, in a ferrimagnetic insulator/nonmagnetic metal/heavy metal system in the diffusive regime. The magnitude of both SMR and REMR decreases with increasing thickness of the interlayer because of the current shunting effect and the reduction in spin accumulation across the interlayer. The latter contribution is due to driving a spin current and persists even in the absence of spin relaxation, which is essential for understanding the magnetoresistance ratio in trilayer structures.

Influence of an electric field on the ferromagnetic resonance in a plane-layered magnetic system

The influence of an electric field on the ferromagnetic resonance (FMR) in a multilayer magnetic system consisting of two magnetic layers separated by a thin nonmagnetic interlayer has been investigated. It has been shown that, upon the excitation of magnetization oscillations by a microwave magnetic field, the eigenfrequencies of the ferromagnetic resonance depend on the stationary electric field applied in the plane of the layers. It has also been demonstrated that, in this system, high-frequency magnetization oscillations can be excited by an electric microwave field. The results of the investigation of the polarization properties of the excitation mechanism indicate that this effect can be observed experimentally.

Using magnetic resonance characteristics to model the structure of multilayer composite nanosystems

The magnetic resonance characteristics of multilayer composite nanosystems with dielectric, semiconductor, and metal nonmagnetic interlayers are investigated. Analysis of the experimental data shows that the dominant factor determining the magnetic resonance characteristics of multilayer composite nanosystems is the shape of their magnetic granules.

Iridium containing honeycomb Delafossites by topotactic cation exchange.

We report the structure and magnetic properties of two new iridium-based honeycomb Delafossite compounds, Cu3NaIr2O6 and Cu3LiIr2O6, formed by a topotactic cation exchange reaction. The starting materials Na2IrO3 and Li2IrO3, which are based on layers of IrO6 octahedra in a honeycomb lattice separated by layers of alkali ions, are transformed to the title compounds by a topotactic exchange reaction through heating with CuCl below 450 °C; higher temperature reactions cause decomposition. The new compounds display dramatically different magnetic behavior from their parent compounds - Cu3NaIr2O6 has a ferromagnetic like magnetic transition at 10 K, while Cu3LiIr2O6 retains the antiferromagnetic transition temperature of its parent compound but displays significantly stronger dominance of antiferromagnetic coupling between spins. These results reveal that a surprising difference in the magnetic interactions between the magnetic Ir ions has been induced by a change in the non-magnetic interlayer species. A combination of neutron and X-ray powder diffraction is used for the structure refinement of Cu3NaIr2O6 and both compounds are compared to their parent materials.

Magnetic and Magnetoresonance Studies of Composite Multilayer Films with Different Kinds of Interlayers

Static magnetic properties, ferromagnetic resonance (FMR) and glancing angle X-ray diffraction spectra (GAXRD) of (CoFeB)/(nonmagnetic interlayer) nanosystems have been studied for three kinds of interlayers: dielectric (SiO2) and semiconductors (Si and SiC). Matter of discussion is the role of the interlayer material in forming of inner structure of magnetic layers and magnetization curve shape.

A theoretical investigation of Ferromagnetic Resonance Linewidth and damping constants in coupled trilayer and spin valve systems

The ferromagnetic resonance intrinsic field linewidth ΔH is investigated for a multilayer system such as a coupled trilayer and a spin valve structure. The magnetic coupling between two ferromagnetic layers separated by a nonmagnetic interlayer will be described by the bilinear J1 and biquadratic J2 coupling parameters. The interaction at the interface of the first ferromagnetic layer with the antiferromagnetic one is account for by the exchange anisotropy field, HE. A general formula is derived for the intrinsic linewidth ΔH. The explicit dependence of ΔH with HE, J1 and J2 will be highlighted. Analytical expressions for each mode field linewidth are found in special cases. Equivalent damping constants will be discussed.

Manipulation of magnetic vortex parameters in disk-on-disk nanostructures with various geometry.

Magnetic nanostructures in the form of a sandwich consisting of two permalloy (Py) disks with diameters of 600 and 200 nm separated by a nonmagnetic interlayer are studied. Magnetization reversal of the disk-on-disk nanostructures depends on the distance between centers of the small and big disks and on orientation of an external magnetic field applied during measurements. It is found that manipulation of the magnetic vortex chirality and the trajectory of the vortex core in the big disk is only possible in asymmetric nanostructures. Experimentally studied peculiarities of a motion path of the vortex core and vortex parameters by the magneto-optical Kerr effect (MOKE) magnetometer are supported by the magnetic force microscopy imaging and micromagnetic simulations.

Reconfigurable and non-volatile vertical magnetic logic gates

In this paper, we discuss the concept and prototype fabrication of reconfigurable and non-volatile vertical magnetic logic gates. These gates consist of two input layers and a RESET layer. The RESET layer allows the structure to be used as either an and or an or gate, depending on its magnetization state. To prove this concept, the gates were fabricated using a multi-layered patterned magnetic media, in which three magnetic layers are stacked and exchange-decoupled via non-magnetic interlayers. We demonstrate the functionality of these logic gates by conducting atomic force microscopy and magnetic force microscopy (MFM) analysis of the multi-layered patterned magnetic media. The logic gates operation mechanism and fabrication feasibility are both validated by the MFM imaging results.

Interlayer interaction in three-layer films obtained by chemical deposition

The results from experimental investigations on the dependences of the displacement field of hysteresis loop HE and the saturation field of the polar Kerr effect HS on the thickness of nonmagnetic interlayers in three-layer films obtained by chemical deposition are presented. Possible mechanisms responsible for oscillating variations in HS at interlayer thicknesses are presented.

Micromagnetic studies on measurements of crystalline anisotropy and magnetostriction in disk media

Measurements of intrinsic magnetic parameters are important in the study of magnetic devices. A micromagnetic model is set up for a perpendicular disk media, including a recording layer (RL, CoCrPt-SiO2, 6 nm), a 12-nm nonmagnetic interlayer and an amorphous soft underlayer (a-SUL, FeCo, 42 nm), in order to study the measurement methods of the crystalline anisotropy and magnetostriction constants in the RL. The effects of the a-SUL on the magnetic properties of the RL are studied by calculating the hysteresis loops. The contributions of the RL and a-SUL to the torque curves of the whole media are calculated respectively. If the intrinsic stress at the interface between the RL and interlayer is along one of the in-plane directions, the crystalline anisotropy constant K1 and magnetostriction field Hms can be determined simultaneously from the simulated in-plane torque curves.

Two-Threshold Stability Loss in Magnetic System with Nonmagnetic Interlayer

In present paper the magnetization of magnetic film consisting of two soft magnetic layers separated by a nonmagnetic interlayer is considered. The film is applied to stiff magnetic substrate. To obtain boundary conditions at the boundary between soft magnetic layers we introduce effective constant of interlayer interaction.

Structure of two-dimensional domain walls in two-layer permalloy films with a nonmagnetic interlayer

Structure of domain walls in two-layer Permalloy films separated by a nonmagnetic interlayer has been studied by the numerical minimization of the functional of the total energy of the domain wall in terms of a two-dimensional model of the magnetization distribution with an exact allowance for basic interactions (including exchange, magnetoanisotropic, and dipole-dipole interactions). Differences between the structure of these walls and that of single-layer films of analogous thicknesses have been investigated. The total energy (and its exchange and dipole-dipole components) per unit area of the surface of domain walls in two-layer films has been calculated as functions of the thicknesses of the Permalloy layers and the interlayer. The dependence of the thickness of magnetic layers at which there occurs a transition from the walls of the same type as in single-layer films of the corresponding thickness to walls of another type on the thickness of the interlayer has also been constructed. A comparison of the curve of this dependence with the experimental data is carried out.

Magnetic aftereffect in Co-P trilayer films

This paper reports on the results of experimental investigations of the magnetic properties of a trilayer system that consists of high-coercive polycrystalline and low-coercive amorphous magnetic Co-P layers and a nonmagnetic amorphous Ni-P interlayer. It has been established that the coercive force and the bias field of the hysteresis loop of the low-coercive layer undergo anomalous changes in the range of small thicknesses of the hard magnetic layer. In the same range of thicknesses, a magnetic aftereffect is found to manifest itself, which is unusual for this type of magnetic structures. The observed features are associated primarily with the kinetics of formation of a crystal structure of the high-coercive layer.

Combined analysis of static and dynamic magnetic characteristics of multilayer CoFeZr/α-Si nanostructures

The combined method of static and dynamic magnetic measurements is used to study nano-dimensional multilayer amorphous CoFeZr/α -Si films. It is established that at the thickness of magnetic layers x = 5–12 nm their magnetization does not differ from that of the bulk material. It is shown that as x is lowered to 2–3 nm, the magnetization of magnetic layers decreases, which may be due to the formation of mixed layers containing nonmagnetic silicides. At a thickness of nonmagnetic interlayers of less than 1 nm the features characteristic of a weak antiferromagnetic interaction of neighboring layers are observed.

First-principles modeling of the magneto-optical response in inhomogeneous systems

We develop an ab initio computational approach to calculate the magneto-optical Kerr effect spectra of layered and nanogranular compounds as a function of several structural and geometrical parameters: (i) composition, (ii) film thickness, and (iii) position, thickness, and number of the nonmagnetic interlayers. The case of nanoparticles in a matrix is treated within the effective-medium approximation and compared to a model (alternating composition layers approximation) that considers different compounds in a thin-film multilayered structure. The magneto-optical filter-amplifier effect of a nonmagnetic overlayer or interlayer and the dependence of the Kerr response on the specific sample composition suggest that our computational approach is a good starting point to build up structures with the desired magneto-optical characteristics and can be used to interpret experimental spectra to single out the microscopic structure and composition of the sample. The model is applied to the Mn-Ge binary system, considering both ${\text{Mn}}_{5}{\text{Ge}}_{3}$ as a film or in a nanoparticle arrangement and ${\text{Mn}}_{x}{\text{Ge}}_{1\ensuremath{-}x}$ diluted semiconductor as possible phases in pure form or intermixed with Ge.

Exchange bias investigations in FeMn based multilayers

We have carried out a systematic investigation of the development of exchange bias in an NiFe/FeMn/NiFe trilayer and in a trilayer with a nonmagnetic interlayer, in order to understand the development of bias in FeMn-based rf magnetron-sputtered multilayers. The trilayer shows two bias loops corresponding to the two NiFe layers where the seed layer shows a greater bias. The bias shows the expected 1/t variation with increasing seed layer thickness. The bias for the top NiFe layer of 5 nm constant thickness increases initially in the 2–6-nm range to reach a maximum value, and thereafter shows a surprising increase in bias at larger seed-layer thicknesses. The introduction of an Al layer of increasing thickness at the top FeMn surface causes the vanishing of the bias for the top NiFe layer and an increase in bias for the seed layer up to 1-nm thickness of Al layer and a decrease thereafter. The seed layer interestingly shows greater bias when an Al layer is present.