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

我们请求资金购买一台量子设计超导量子干涉器件 (SQUID) 磁力计，以测量在掺杂和未掺杂的 AlGaN/GaN 异质结构和单晶锰基钙钛矿上生长的锰和铬掺杂的 III 族氮化物薄膜的磁特性。我们的实验室配备了所有的生长、制造、电气和结构测试能力，但缺少这一关键设备。该设备将安装在弗吉尼亚联邦大学最先进的弗吉尼亚微电子中心研究实验室。在 GaN:Mn 的室温铁磁性以及自旋电子学框架下将自旋和电荷传输相结合的器件潜在应用的推动下，我们将研究纳米级半导体铁磁体的基本问题，例如与 GaMnN/GaCrN 薄膜连接的 GaN 量子点以及与 GaN 薄膜连接的 GaMnN 或 GaCrN 点中的磁性热稳定性、居里温度、磁粘性、矫顽力以及点间磁相互作用。此外，我们还将研究单晶氧化物的磁性，这些单晶氧化物是在我们的实验室中使用 MBE 系统和溅射系统生产的。具体来说，将测量场冷却和零场冷却条件下磁化强度的温度依赖性、磁化磁滞和磁弛豫相关行为。这些对于理解这些铁磁半导体和磁性钙钛矿的磁性行为至关重要。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取向。由于磁矩的绝对大小非常小，特别是在较高温度下，包含几层稀释磁性材料的薄膜系统的行为变得复杂。为了高精度测量这些效应并获得制造高质量样品的相关信息，我们需要配备样品空间烤箱和样品旋转器的SQUID磁力计。该提案的智力价值是通过对使用最先进技术制造的稀磁半导体和磁性氧化物的磁化特性的精确测量，提供对基于自旋的器件上磁自旋行为的物理学的基本和技术理解。该提案更广泛的影响是为自旋电子器件的制造提供必要的信息和反馈，寻找新的磁性材料以实现更好的自旋注入，以及了解这类新型铁磁半导体的自旋自由度。

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.