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

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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.