MRI: Acquisition of SQUID Magnetometer for Ferromagnetic Semiconductor and Oxide Research

我们请求资金购买Quantum Design超导量子干涉器件(SQUID)磁强计，以测量在掺杂和非掺杂的AlGaN/GaN异质结和单晶锰基钙钛矿上生长的掺锰和掺铬的III族氮化物薄膜的磁性。我们的实验室配备了所有的生长、制造、电气和结构能力测试，但这一关键设备缺失。该设备将安装在弗吉尼亚大学弗吉尼亚微电子中心最先进的研究实验室中。受GaN：Mn的室温铁磁性和自旋电子学和电荷输运相结合的潜在应用的启发，我们将研究纳米半导体铁磁材料的基本问题，如磁性的热稳定性、居里温度、磁粘度、矫顽力以及GaN量子点与GaMnN/GaCrN薄膜以及GaMnN或GaCrN量子点与GaN薄膜界面的相互作用。此外，我们还将研究单晶氧化物的磁性，这是我们实验室使用分子束外延系统和溅射系统生产的。具体地，将测量在场冷和零场冷条件下的磁化强度与温度的关系、磁化滞后和与磁弛豫有关的行为。这些对于理解这些铁磁性半导体和磁性钙钛矿的磁性行为是至关重要的。此外，还将研究与空穴密度或外延生长晶格匹配应变相关的磁各向异性和易轴重新定向。由于磁矩的绝对值很小，特别是在较高的温度下，含有几层稀磁材料的薄膜系统的行为很复杂。为了高精度地测量这些效应并获得制造高质量样品所需的相关信息，我们需要一台配备样品空间烤箱和样品旋转器的SQUID磁强计。该方案的智能优点是通过精确测量稀磁半导体和使用最先进技术制造的磁性氧化物的磁化性质，为自旋器件上的磁自旋行为提供基本的和技术上的理解。这项提议的更广泛的影响是提供必要的信息和反馈，关于自旋电子器件的制造，寻找新的磁性材料来更好地进行自旋注入，以及了解这类新的铁磁半导体中的自旋自由度。

We request funds to acquire a Quantum Design Superconducting Quantum Interference Device(SQUID) magnetometer to measure the magnetic properties of Mn and Cr-doped Group III-nitride films grown on both doped and undoped AlGaN/GaN heterostructures and singlecrystalline Mn-based perovskites. Our laboratories are equipped with all the growth, fabrication,testing for electrical and structural capabilities, but this critical piece of equipment is missing. Theequipment will be installed in the state of the art Virginia Microelectronic Center researchlaboratories at VCU. Spurred by room temperature ferromagnetism in GaN:Mn and potentialapplications combining spin and charge transport for devices under the umbrella of spintronics,we will investigate the fundamental issues in nanoscale semiconducting ferromagnets, such asthermal stability of magnetism, Curie temperature, magnetic viscosity, coercivity, and inter-dotmagnetic interactions in GaN quantum dots interfaced with GaMnN/GaCrN films, as well asGaMnN or GaCrN dots interfaced with GaN films. Additionally, we will also investigatemagnetism in single crystalline oxides, which are produced in our laboratory using MBE systemsand a sputtering system. Specifically, the temperature dependence of magnetization in both field-cooled and zero-field-cooled conditions, magnetization hysteresis and magnetic relaxation relatedbehavior will be measured. These are critical to understand the magnetic behavior of theseferromagnetic semiconductors and magnetic perovskites.Furthermore, magnetic anisotropy and easy axis reorientations related to hole density or epitaxialgrowth lattice-matching strains will be investigated. The behavior of thin film systems containinga few layers of diluted magnetic materials is complicated by the fact that the absolute magnitudeof the magnetic moment is very small, especially at higher temperatures. In order to measurethese effects with high precision and obtain the relevant information for fabricating high-qualitysamples, we need a SQUID magnetometer equipped with sample space oven and sample rotator.The intellectual merit of the proposal is to provide basic and technological understanding ofphysics of behavior of magnetic spins on spin-based devices from the precise measurement ofmagnetization properties on dilute magnetic semiconductors and magnetic oxides fabricated usingthe state-of-the-art techniques. The broader impacts of this proposal are to provide necessaryinformation and feedback on the fabrication of spinotronic devices, search for new magneticmaterials for better spin-injection, and understanding of spin degrees of freedom in this new classof ferromagnetic semiconductors.