Electric-field-tunable linear unipolar magnetic switch based on a spin-valve multiferroic heterostructure

This work reports an energy-efficient strategy for realizing linear unipolar giant magnetoresistance (GMR) switch by using electric fields (E-fields). Herein, a modified spin-valve (SV) structure of double antiferromagnetic (AFM) pinning layers was adopted. Since the magnetization direction of ferromagnetic (FM) layer can be controlled via the strain-mediated magnetoelectric (ME) effect, a multiferroic heterostructure of SV/PMN-PT was fabricated. By applying an E-field on the PMN-PT substrate, an effective magnetic field Heff was produced along the [1-10] direction of PMN-PT. It can turn the magnetic moments of FM layer toward [1-10] direction. Accordingly, a linear GMR curve with a wide sensing field range was achieved. This E-field-induced linear magnetic switch can satisfy the demand for different switching field ranges in the same application system.

Orthogonal interlayer coupling in an all-antiferromagnetic junction

The interlayer coupling of two ferromagnetic layers results in found of giant magnetoresistance, which forms the foundation of spintronics and accelerates the development of information technology. Compared with ferromagnets, antiferromagnets (AFMs) possess huge potential in ultrafast and high-density data processing and information storage because of their terahertz spin dynamics and subtle stray field. The interlayer coupling in AFMs has long been neglected, because the collinear parallel and antiparallel arrangements of AFMs are indistinguishable. However, the noncollinear interlayer coupling in AFMs is detectable, and can be a potential candidate for practical antiferromagnetic spintronic devices. Here we demonstrate orthogonal interlayer coupling at room temperature in an all-antiferromagnetic junction Fe2O3/Cr2O3/Fe2O3, where the Néel vectors in the top and bottom functional materials Fe2O3 are strongly orthogonally coupled and the coupling strength of which is significantly affected by the thickness of the antiferromagnetic Cr2O3 spacer. From the energy and symmetry analysis, the direct coupling via uniform magnetic ordering is excluded. The coupling is proposed to be mediated by quasi-long range order in the spacer. Besides the fundamental significance, the strong coupling in an antiferromagnetic junction makes it a promising building block for practical antiferromagnetic spintronics with high-speed operation and ultrahigh-density integration.

Analysis of current-in-plane giant magnetoresistance using Co2FeAl0.5Si0.5 half-metallic Heusler alloy

Current-in-plane giant magnetoresistance (CIP-GMR) devices receive revived interest for high-sensitivity magnetic sensors. However, further improvement in MR ratios is necessary to achieve sufficiently magnetic field sensitivity. The usage of half-metallic Co-based Heusler alloy ferromagnetic (FM) layer has been demonstrated to be effective in enhancing GMR in current-perpendicular-to-plane (CPP) configuration; however, only small MR ratios are obtained in the CIP configuration. To understand the origin of the disappointingly low MR in the CIP configuration using the Heusler alloy FM layers, we investigated magnetotransport properties of CIP-GMR devices using half-metallic Co2FeAl0.5Si0.5 (CFAS) Heusler alloy and conventional CoFe alloy as ferromagnetic (FM) layers in combination with Ag or Cu as nonmagnetic (NM) spacer layer. Regardless of high lattice and electronic band matching at the CFAS/Ag interface, CFAS/Ag CIP spin valves (SVs) shows the MR ratio of only 1.2% at RT, which is much smaller than those of reference CoFe/Cu and CoFe/Ag SVs, 21.6 and 8.4%, respectively. Current density distribution simulations suggest that large current shunting occurs in the Ag layer due to significant resistivity gap between CFAS and Ag, which limits the generation of highly spin-polarized current from the CFAS layer, resulting in the very small MR ratios. To enhance the MR ratio in CIP-GMR using half-metallic materials, resistivity matching between FM layers and NM layer is required in addition to the high electronic band match that has been considered as key factors to obtain high MR ratio in CIP-GMR.

Ultrahigh Spin Filter Efficiency, Giant Magnetoresistance and Large Spin Seebeck Coefficient in Monolayer and Bilayer Co-/Fe-/Cu-Phthalocyanine Molecular Devices

The spin related electrical and thermoelectric properties of monolayer and bilayer MPc (M = Co, Fe, Cu) molecular devices in a parallel spin configuration (PC) and an anti-parallel spin configuration (APC) between the V-shaped zigzag-edged graphene nanoribbon electrodes and the center bilayer MPc molecules are investigated by combining the density functional theory and non-equilibrium Green’s function approaches. The results show that there is an ultrahigh spin filter efficiency exceeding 99.99995% and an ultra-large total conductance of 0.49996G0 for FePc-CoPc molecular devices in PC and a nearly pure charge current at high temperature in an APC and a giant MR ratio exceeding 9.87 × 106% at a zero bias. In addition, there are pure spin currents for CuPc and FePc molecular devices in PC, and an almost pure spin current for FePc molecular devices in an APC at some temperature. Meanwhile, there is a high SFE of about 99.99585% in a PC and a reserved SFE of about −19.533% in an APC and a maximum MR ratio of about 3.69 × 108% for the FePc molecular device. Our results predict that the monolayer and bilayer MPc (M = Co, Fe, Cu) molecular devices possess large advantages in designing high-performance electrical and spintronic molecular devices.

PROSPECTION: HOW SPINTRONICS WILL AFFECT MACHINE VISION

The article describes a look into the future, about how spintronics will affect machine vision. The authors describe the electron spin, the effect of giant magnetoresistance, and the device of spin diodes. Creating compact devices in the field of nanoelectronics creates a problem of high energy consumption. Relatively recently formed science – spintronics – allows you to reduce costs. It is known that the electron is the carrier of an elementary charge, and this property is based on the operation of all electronic devices. However, this particle is also characterized by the presence of its own angular momentum, i.e., spin. This causes the existence of a magnetic field around the electron. The effect of giant magnetoresistance also plays an important role. This phenomenon is considered the basis of spintronics and consists of the following. When a current flows through a structure that has several alternating layers, its resistance may vary depending on the nature of the magnetization of each layer in relation to each other.