Mesoscopic effects in ferromagnetic materials

Nanoparticle;Ferromagnet;Domain wall;Weak localization;Phase coherent;Mesoscopic transport

Liu, Xiya ; Physics

University:Georgia Institute of Technology

Department:Physics

关键词: Nanoparticle;    Ferromagnet;    Domain wall;    Weak localization;    Phase coherent;    Mesoscopic transport;   

Others  :  https://smartech.gatech.edu/bitstream/1853/24669/1/liu_xiya_200808_phd.pdf

美国|英语

来源: SMARTech Repository

【 摘 要 】

Mesoscopic effects in ferromagnets could be different from mesoscopic effects in normal metals. While normal metals with a short mean-free-path do not exhibit classical magnetoresistance, weakly disordered ferromagnets with a similar mean-free-path display magnetoresistance including domain wall resistance (DWR) and anisotropic magnetoresistance (AMR). Magnetoresistance could lead to novel mesoscopic effects because the wave function phase depends on the scattering potential. In this thesis, we present our measurements of mesoscopic resistance fluctuations in cobalt nanoparticles and study how the fluctuations with bias voltage, bias fingerprints, respond to magnetization-reversal processes. The resistance has been found to be very sensitive to the magnetic state of the sample. In particular, we observe significant wave-function phase shifts generated by domain walls, and it is explained by mistracking effect, where electron spins lag in orientation with respect to the moments inside the domain wall. Short dephasing length and dephasing time are found in our Co nanoparticles, which we attribute to the strong magnetocrystalline anisotropy.