Search

Multiferroic materials have great potential in non-volatile devices for low-power and ultra-high density information storage, owing to their unique characteristic of coexisting ferroelectric and ferromagnetic orders. The effective manipulation of their intrinsic anisotropy makes it promising to control the multiple degrees of freedom of the storage "medium". Here, we have discovered intriguing electrical and magnetic anisotropies within the intralayer of CuCrP2S6, a promising van der Waals multiferroic material. The in-plane uniaxial anisotropies of the current rectifications, magnetic properties and magnon modes are demonstrated and manipulated by electric direction/polarity, temperature variation and magnetic field. More important, we have observed spin-flop transition corresponding to specific magnon modes, and it is well supported by theoretical calculations. Our work provides the first observation of electrical and magnetic anisotropies with same easy axis in van der Waals multiferroics, which will stimulate novel device applications of artificial bionic synapses, multi-terminal spintronic chips and magnetoelectric devices.

Rare-earth-transition-metal (RETM) ferrimagnets have received great attention for their small magnetic moments and fast dynamics in the development of next-generation spintronic devices. Here, we study spin Hall magnetoresistance (SMR) in the RETM ferrimagnet and heavy-metal bilayers of ${\mathrm{Co}}_{1\text{\ensuremath{-}}x}{\mathrm{Tb}}_{x}/\mathrm{Pt}$. Anomalous temperature dependence of the SMR is observed, where the SMR changes nonmonotonically and has a valley next to the magnetization compensation temperature. Additionally, we find that the SMR varies significantly for different chemical compositions of ${\mathrm{Co}}_{1\text{\ensuremath{-}}x}{\mathrm{Tb}}_{x}$ alloys. These anomalous behaviors are interpreted as the dramatically altered spin polarization of the ${\mathrm{Co}}_{1\text{\ensuremath{-}}x}{\mathrm{Tb}}_{x}$ layer near the compensation point. By deducing spin polarization from the abnormal temperature dependence of SMR, we provide a convenient way to access spin polarization of the RETM ferrimagnets. These experimental results show implications for tunable spin-current sources of RETM ferrimagnets.

The topological material of $\mathrm{C}{\mathrm{o}}_{2}\mathrm{MnGa}$ with potentially high spin polarization has attracted more and more attention, in the fields of fundamental science and spintronic applications. Here we report the electrical- and magnetotransport behaviors in epitaxial $\mathrm{C}{\mathrm{o}}_{2}\mathrm{MnGa}$ thin films. An angle-independent negative linear magnetoresistance and a negative anisotropy magnetoresistance are observed in the whole temperature range from 3 to 300 K, indicating the existence of weak spin disorder and a high spin polarization. Intriguingly, with decreasing temperature an anomalous resistivity upturn that exhibits $\ensuremath{-}{T}^{1/2}$ dependence is observed, and this phenomenon is robust under magnetic fields. Further analysis demonstrates that the three-dimensional enhanced electron-electron interaction effect is responsible for these phenomena rather than the orbital two-channel Kondo effect or other quantum interference effects, which provides deeper insight into the transport behavior of the $\mathrm{C}{\mathrm{o}}_{2}\mathrm{MnGa}$ materials.

Compensated ferrimagnetic materials such as Co–Tb and Co–Gd have been confirmed to have significant spin–orbit torque (SOT) efficiency. However, the large coercivity and a relatively small spin-mixing conductance may hinder the applications of the near compensated ferrimagnets. In this work, we investigate the SOT effect and its potential applications in Ta/Co–Tb/Pt heterostructures. Based on a Co-rich ferrimagnetic alloy, we obtain a significant SOT switching efficiency of 15 ± 1 (10−6 Oe cm2/A) and a considerable effective spin Hall angle of θ eff = 0.270 ± 0.005. Using harmonic Hall measurement, the temperature dependence of the damping-like effective field has been extracted. The SOT efficiency scales linearly with 1/Ms in the high-temperature range but significantly deviates from this linear scaling law at a lower temperature, which is near the compensation point. In the Tb rich Ta/Co–Tb/Pt SOT device, we demonstrate the functionality of a neuron and the dependence of firing possibility on the intensity of coming stimulus, which is mimicked by the SOT switching dynamics in the ferrimagnetic Co–Tb alloy.

The effects of Ga composition on the electrical parameters of (Al,Ga)Sb/InAs two-dimensional electron gas have been investigated. The (Al,Ga)Sb/InAs structures are grown on GaAs (001) substrate by molecular-beam epitaxy with various Ga compositions in Al1−x Ga x Sb bottom barrier. The sheet resistance shows a crossover with the variation of temperature, and the temperature T* corresponding to this crossover decreases with increasing the Ga composition. The temperature dependence of the electron mobility is similar for the samples with different Ga compositions, while the temperature dependence of the carrier density is obviously different. Qualitative analyses reveal that the temperature dependent portion of carrier density is mainly determined by the interface-related donors. A thermal activation model is used to fit the temperature dependence of carrier density, and the fitting results imply that the thermal activation energies of the carriers are significantly affected by the Ga composition. Our results provide useful information for understanding the sources of carriers in the (Al,Ga)Sb/InAs systems, and provide one pathway for the modulation of the temperature dependent carrier density.

We have investigated the magneto-transport properties of an off-stoichiometric full-Heusler alloy Co2MnAl single-crystalline film. The Co1.65Mn1.35Al (CMA) film epitaxially grown on Ⅲ–Ⅴ semiconductor GaAs substrate exhibits perpendicular magnetic anisotropy. The resistivity of the CMA film increases with the temperature T decreasing from 300 to 5 K, showing a semiconducting-like transport behavior. Different activation energies are found in three temperature regions with transition temperatures of 35 and 110 K. In the meanwhile, the remanent magnetization can be described by T 3/2 and T 2 laws in the corresponding medium and high T ranges, respectively. The transition at around 110 K could be attributed to the ferromagnetism evolving from localized to itinerant state. The Curie temperature of the CMA film is estimated to be ~640 K. The intrinsic anomalous Hall conductivity of ~55 Ω–1cm–1 is obtained, which is almost twenty times smaller than that of Co2MnAl.