Cubic MnSb: epitaxial growth of a predicted room temperature half-metal
James D. Aldous, Christopher W. Burrows, Ana M. Sánchez, Richard Beanland, Ian Maskery, Matthew K. Bradley, Manuel dos Santos Dias, Julie B. Staunton, Gavin R. Bell
Epitaxial films including bulk-like cubic and wurtzite polymorphs of MnSb have been grown by molecular beam epitaxy on GaAs via careful control of the Sb4/Mn flux ratio. Nonzero-temperature density functional theory was used to predict ab initio the spin polarization as a function of reduced magnetization for the half-metals NiMnSb and cubic MnSb. In both cases, half-metallicity is lost at a threshold magnetization reduction, corresponding to a temperature T*< Tc. This threshold is far higher for cubic MnSb compared to NiMnSb and corresponds to T* > 350K, making epitaxial cubic MnSb a promising candidate for room temperature spin injection into semiconductors.
Magnetic topological insulators such as MnBi2Te4 and MnSb2Te4 are promising hosts of novel physical phenomena such as quantum anomalous Hall effect and intrinsic axion insulator state, both potentially important for the implementation in topological spintronics and error-free quantum computing. In the bulk, the materials are antiferromagnetic but appropriate stacking with non-magnetic layers or excess Mn in the crystal lattice can induce a net ferromagnetic alignment. In this work we report the growth of (Sb2Te3)x(MnSb2Te4)y layers with varying Mn content by molecular beam epitaxy. The Mn flux…
We have studied the properties of relatively thick (about 120 nm) magnetic composite films grown by pulsed laser deposition method using (GaSb)$_{0.59}$(MnSb)$_{0.41}$ eutectic compound as a target for sputtering. For the studied films we have observed ferromagnetism and anomalous Hall effect above the room temperature, it manifests the presence of spin-polarized carriers. Electron microscopy, atomic and magnetic force microscopy results suggests that films under study have homogenous columnar structure in the bulk while MnSb inclusions accumulate near it's surface. This is in good agreement w…
Room temperature spin filtering in epitaxial cobalt-ferrite tunnel barriers
我们报告的直接实验证据，室温自旋过滤的磁性隧道结（MTJ）含有CoFe 2 O 4隧道势垒通过隧道磁阻（TMR）测量。Pt（111）/CoFe_2 O_4（111）/γ-Al_2 O_3（111）/Co（0001）全外延MTJ的生长是为了获得能够在室温下工作的高质量系统。自旋极化输运测量显示，在2K和290 K下，TMR值分别为-18%和-3%。此外，TMR比遵循一个独特的偏置电压依赖性，这在理论上已经被预测为在MTJ中包含磁势垒的自旋过滤的签名。因此，CoFe 2 O 4隧道势垒提供了一个模型系统，以调查在很宽的温度范围内的自旋过滤。
Ferromagnetic insulators (FMIs) are one of the most important components in developing dissipationless electronic and spintronic devices. However, since ferromagnetism generally accompanies metallicity, FMIs are innately rare to find in nature. Here, novel room-temperature FMI films are epitaxially synthesized by deliberate control of the ratio of two B-site cations in the double perovskite Sr2FeReO6. In contrast to the known ferromagnetic metallic phase in stoichiometric Sr2FeReO6, a FMI state with a high Curie temperature (Tc~400 K) and a large saturation magnetization (MS~1.8 μB/f.u.) is fo…
Multiferroic materials open up the possibility to design novel functionality in electronic devices, with low energy consumption. However, there are very few materials that show multiferroicity at room temperature, which is essential to be practically useful. AlxFe2-xO3 (x-AFO) thin films, belonging to the k-Al2O3 family are interesting because they show room temperature ferrimagnetism and have a polar crystal structure. However, it is difficult to realise its ferroelectric properties at room temperature, due to low resistivity of the films. In this work, we have deposited x-AFO (0.5 <= x <= 1)…
Magnetic properties of epitaxial Fe$_3$O$_4$ films with various crystal orientations and TMR effect in room temperature
Fe $_3$ O $_4$是在室温（RT）下表现出导电性的亚铁磁性尖晶石铁氧体。虽然根据从头计算已经预测该材料是半金属，但是具有Fe $_3$ O $_4$电极的磁性隧道结（MTJ）已经证明了小的隧道磁阻效应。甚至连TMR比率的符号都没有在实验中确定。在这里，我们报告的磁性外延Fe $_3$ O $_4$薄膜与各种晶体取向。薄膜的磁滞曲线显示出明显的晶体取向依赖性。特别地，Fe $_3$ O $_4$（110）膜表现出面内单轴磁各向异性。对于磁滞回线的矩形度，Fe $_3$ O $_4$（111）表现出最大的矩形度。此外，我们还制备了Fe $_3$ O $_4$（110）电极的MTJ，在室温下获得了-12\%的TMR效应。负的TMR比对应于能带计算预测的Fe $_3$ O $_4$的负自旋极化。
Room-temperature quantum oscillations of static magnetic susceptibility of silicon-carbide epitaxial layers grown on a silicon substrate by the method of the coordinated substitution of atoms
Giant tunnel magnetoresistance (TMR) ratios of 417% at room temperature (RT) and 914% at 3 K were demonstrated in epitaxial Fe/MgO/Fe(001) exchanged-biased spin-valve magnetic tunnel junctions (MTJs) by tuning growth conditions for each layer, combining sputter deposition for the Fe layers, electron-beam evaporation of the MgO barrier, and barrier interface tuning. Clear TMR oscillation as a function of the MgO thickness with a large peak-to-valley difference of ~80% was observed when the layers were grown on a highly (001)-oriented Cr buffer layer. Specific features of the observed MTJs are s…
Future spintronics requires the realization of thin film of half-metallic ferromagnets having high Curie temperature and 100\% spin polarization at the Fermi level for potential spintronics applications. In this paper, we report the epitaxial thin films growth of half-metallic CoFeMnGe Heusler alloy on MgO (001) substrate using pulsed laser deposition system, along with the study of structural, magnetic and transport properties. The magnetic property measurements of the thin film suggest a soft ferromagnetic state at room temperature with an in-plane magnetic anisotropy and a Curie temperature…
Room-temperature magnetoelectric multiferroicity has been observed in c-axis oriented GaFeO$_3$ thin films (space group $Pna2_1$), grown on economic and technologically important (100)Si substrates by pulsed laser deposition technique. Structural analysis and comprehensive mapping of Ga:Fe ratio across a length scale range of 10$^4$ reveal coexistence of epitaxial and chemical strain. It induces formation of finer magnetic domains and large magnetoelectric coupling - decrease in remanent polarization by $\sim$21\% under $\sim$50 kOe. Magnetic force microscopy reveals presence of both finer ($<…
Single-phase multiferroic materials that allow the coexistence of ferroelectric and magnetic ordering above room temperature are highly desirable, motivating an ongoing search for mechanisms for unconventional ferroelectricity in magnetic oxides. Here, we report an antisite defect mechanism for room temperature ferroelectricity in epitaxial thin films of yttrium orthoferrite, YFeO3, a perovskite-structured canted antiferromagnet. A combination of piezoresponse force microscopy, atomically resolved elemental mapping with aberration corrected scanning transmission electron microscopy and density…
Epitaxial growth of multiferroic Pb(Zr0.57Ti0.43)O3-Pb(Fe2/3W1/3)O3 solid-solution thin films and their magnetoelectric effects
本文报道了用脉冲激光沉积法外延生长单相[Pb（Zr 0.57 Ti 0.43）O3]0.8[Pb（Fe 2/3 W 1/3）O3]0.2（PZT-PFW）固溶体薄膜。X射线衍射测试表明薄膜具有四方晶系结构。该薄膜在室温下表现出铁电性和弱铁磁响应。磁电效应进行了研究，非线性磁电系数进行了测量，发现是可比的多铁性六方锰氧化物，但至少两个数量级小于多晶PZT-PFW薄膜。
Spin-charge interconversion phenomena at the interface between magnetic materials and topological insulators (TIs) are attracting enormous interest in the research effort towards the development of fast and ultra-low power devices for the future information and communication technology. We report a large spin-to-charge conversion efficiency in Au/Co/Au/Sb2Te3/Si(111) heterostructures based on Sb2Te3 TIs grown by metal organic chemical vapor deposition on 4 inches Si(111) substrates. By conducting room temperature spin pumping ferromagnetic resonance, we measure an inverse Edelstein Effect leng…
Rare-earth orthoferrite RFeO3 materials such as NdFeO3 are strongly studied because of their fascinating magnetic properties and their potential applications. Here, we show the successful epitaxial synthesis of parasitic-free NFO thin film by pulsed laser deposition on (001)-SrTiO3. High-resolution X-ray diffraction shows a coherent growth and a tetragonal-like structure of a tensile strained 80 nm thick NFO film in contrast with the bulk orthorhombic state. Room temperature magnetometry indicates a bulk-like antiferromagnetic state for the NFO film. Temperature-dependent X-ray diffraction and…
SrVO3 thin films with a high figure of merit for applications as transparent conductors were crystallized from amorphous layers using solid phase epitaxy (SPE). Epitaxial SrVO3 films crystallized on SrTiO3 using SPE exhibit a room temperature resistivity of 2.5 x 10-5 Ohms cm, a residual resistivity ratio of 3.8, and visible light transmission above 0.5 for a 60 nm-thick film. SrVO3 layers were deposited at room temperature using radio-frequency sputtering in an amorphous form and subsequently crystallized by heating in controlled gas environment. The lattice parameters and mosaic angular widt…
We investigated perpendicular magnetic anisotropy (PMA) and related properties of epitaxial Fe (0.7 nm)/MgAl2O4(001) heterostructures prepared by electron-beam evaporation. Using an optimized structure, we obtained a large PMA energy ~1 MJ/m3 at room temperature, comparable to that in ultrathin-Fe/MgO(001) heterostructures. Both the PMA energy and saturation magnetization show weak temperature dependence, ensuring wide working temperature in application. The effective magnetic damping constant of the 0.7 nm Fe layer was ~0.02 using time-resolved magneto-optical Kerr effect. This study demonstr…
By inserting a SrZrO$_3$ buffer layer between the film and the substrate, we demonstrate a significant reduction of the threading dislocation density with an associated improvement of the electron mobility in La:BaSnO$_3$ films. A room temperature mobility of 140 cm$^2$ V$^{-1}\text{s}^{-1}$ is achieved for 25-nm-thick films without any post-growth treatment. The density of threading dislocations is only $4.9\times 10^{9}$ cm$^{-2}$ for buffered films prepared on (110) TbScO$_3$ substrates by pulsed laser deposition.
Among the class of strongly-correlated oxides, La1-xSrxMnO3 $-$ a half metallic ferromagnet with a Curie temperature above room temperature $-$ has sparked a huge interest as a functional building block for memory storage and spintronic applications. In this respect, defect engineering has been in the focus of a long-standing quest for fabricating LSMO thin films with highest quality in terms of both structural and magnetic properties. Here, we discuss the correlation between structural defects, such as oxygen vacancies and impurity islands, and magnetism in La0.74Sr0.26MnO3/SrTiO3 (LSMO/STO) …
Mn$_3$Sn is a non-collinear antiferromagnetic quantum material that exhibits a magnetic Weyl semimetallic state and has great potential for efficient memory devices. High-quality epitaxial $c$-plane Mn$_3$Sn thin films have been grown on a sapphire substrate using a Ru seed layer. Using spin pumping induced inverse spin Hall effect measurements on $c$-plane epitaxial Mn$_3$Sn/Ni$_{80}$Fe$_{20}$, we measure spin-diffusion length ($λ_{\rm Mn_3Sn}$), and spin Hall conductivity ($σ_{\rm{SH}}$) of Mn$_3$Sn thin films: $λ_{\rm Mn_3Sn}=0.42\pm 0.04$ nm and $σ_{\rm{SH}}=-702~\hbar/ e~Ω^{-1}$cm$^{-1}$.…
The temperature dependence of the Seebeck coefficient of homoepitaxial metal organic vapor phase (MOVPE) grown, silicon doped $β$-Ga$_2$O$_3$ thin films was measured relative to aluminum. For room temperature we found the relative Seebeck coefficient of $S_{β\text{-Ga}_2\text{O}_3\text{-Al}}=(-300\pm20)\;μ$V/K. At high bath temperatures $T>240$ K, the scattering is determined by electron-phonon-interaction. At lower bath temperatures between $T=100$ K and $T=300$ K, an increase in the magnitude of the Seebeck coefficient is explained in the frame of Strattons formula. The influence of the diff…
Single-photon superradiance can emerge when a collection of identical emitters are spatially separated by distances much less than the wavelength of the light they emit, and is characterized by the formation of a superradiant state that spontaneously emits light with a rate that scales linearly with the number of emitters. This collective phenomena has only been demonstrated in a few nanomaterial systems, all requiring temperatures below 10K. Here, we rationally design a single colloidal nanomaterial that hosts multiple (nearly) identical emitters that are impervious to the fluctuations which …
