Enhanced magnetic anisotropy and high hole mobility in magnetic semiconductor Ga_(1-x-y)Fe_(x)Ni_(y)Sb

(Ga,Fe)Sb is a promising magnetic semiconductor(MS)for spintronic applications because its Curie temperature(T_(C))is above 300 K when the Fe concentration is higher than 20%.However,the anisotropy constant Ku of(Ga,Fe)Sb is below 7.6×10^(3)erg/cm^(3)when Fe concentration is lower than 30%,which is one order of magnitude lower than that of(Ga,Mn)As.To address this issue,we grew Ga_(1-x-y)Fe_(x)Ni_(y)Sb films with almost the same x(≈24%)and different y to characterize their magnetic and electrical transport properties.We found that the magnetic anisotropy of Ga_(0.76-y)Fe_(0.24)Ni_(y)Sb can be enhanced by increasing y,in which Ku is negligible at y=1.7%but increases to 3.8×10^(5)erg/cm^(3)at y=6.1%(T_(C)=354 K).In addition,the hole mobility(μ)of Ga_(1-x-y)Fe_(x)Ni_(y)Sb reaches 31.3 cm^(2)/(V∙s)at x=23.7%,y=1.7%(T_(C)=319 K),which is much higher than the mobility of Ga_(1-x)Fe_(x)Sb at x=25.2%(μ=6.2 cm^(2)/(V∙s)).Our results provide useful information for enhancing the magnetic anisotropy and hole mobility of(Ga,Fe)Sb by using Ni co-doping.

The room temperature ferromagnetism in highly strained twodimensional magnetic semiconductors

In spintronics,it is still a challenge in experiments to realize the ferromagnetic semiconductors with Curie temperature Tc above room temperature.In 2017,the successful synthesis of two-dimensional(2D)van der Waals ferromagnetic semiconductors,including the monolayer CrI3 with Tc=45 K[1]and the bilayer Cr2Ge2Te6 with Tc=28 K[2]in experiments,has attracted extensive attention in the 2D ferromagnetic semiconductors.One of the key problems is to find suitable 2D magnetic semiconductors,which can have room-temperature operation as required in applications.

Artificial neuron and synapse in spintronics devices

Neuromorphic computing is the development of computingschemes inspired by the processing of information in thebrain, which can execute complex tasks very efficiently usingan architecture that is completely different from that of semiconductorchips. Recently, researchers from Tohoku Universityhave realized an artificial neuron and synapse in spintronicsdevices, which are promising for future energy-efficientand adoptive computing systems, as they behave likethe spiking neural network in human brains.

Preface to the Special Issue on Challenges and Possibilities of Magnetic Semiconductors

Magnetic semiconductors have been pursued for over 50 years because they combine two critical components of modern information technology: semiconductors for logic and magnets for memory. Remarkably, boosted by the discovery of ferromagnetism in the (III,Mn)As system two decades ago, magnetic semiconductors have become one of leading material systems which are critical for future applications in energy efficient information technology, quantum computing, and quantum communication. However, after more than a decade of rapid development, the ongoing research in magnetic semiconductors must now face reality:"Is it possible to create magnetic semiconductors that work at room temperature?" To answer this question, great efforts have recently been made in theory and experiments to discover and design new material platforms to host magnetic ions. These recent advances have thus revived our understanding of the field and lifted the field off for a new opportunity.

A crystal graph multilayer descriptor

2D ferromagnetic(FM)materials are crucial for next-generation spintronic devices owing to their atomic thickness and controllable electron/spin degree of freedom.However,due to the diversity of 2D structures and the complexity of magnetism,massive search for 2D FM materials is still a tough task.Recent development of machine learning technique has shown great potential in rapid searching for material with target property in large chemical space.Nevertheless,due to the lack of material data and proper descriptor,searching for 2D FM materials remains a challenge.

Polarization-sensitive and wide-spectrum photovoltaic detector based on quasi-1D ZrGeTe_(4)nanoribbon

Low-dimensional semiconductors with in-plane anisotropy and narrow bandgap have been extensively applied to polarized detection in the near-infrared(NIR)region.However,the narrow bandgap can cause noise owing to the high dark current in photodetectors.This article reports quasi-1D ZrGeTe_(4)nanoribbonbased photodetectors with low dark current and broadband polarization detection.The photodetector was fabricated by evaporating 50-nm-thick Au electrodes on a ZrGeTe_(4)nanoribbon.Benefiting from the photovoltaic characteristics in the ZrGeTe_(4)nanoribbon and Au electrodes,these photodetectors can operate without bias voltage,with decreased dark current,and improved device performance.Furthermore,the quasi-1D ZrGeTe_(4)nanoribbon-based photodetectors demonstrate a polarization sensitivity in a broadband from visible(VIS)to the NIR region,such as a high photoresponsivity of 625.65 mA W1,large external quantum efficiency of 145.9%at 532 nm,and photocurrent anisotropy ratio of 2.04 at 1064 nm.They exhibit a novel perpendicular optical reversal of 90in polarization-sensitive photodetection,angle-resolved absorption spectra,and azimuth-dependent reflectance difference microscopy(ADRDM)from VIS to the NIR region,as opposed to other nanoribbon-based polarization-sensitive photodetectors.This work paves the way for utilizing photovoltaic photodetectors based on low-dimensional materials for broad-spectrum polarized photodetection.