Broadband spectroscopy of thermodynamic magnetization fluctuations through a ferromagnetic spin-reorientation transition.

ABSTRACT: We use scanning optical magnetometry to study the broadband frequency spectra of spontaneous magnetization fluctuations, or "magnetization noise", in an archetypal ferromagnetic film that can be smoothly tuned through a spin reorientation transition (SRT). The SRT is achieved by laterally varying the magnetic anisotropy across an ultrathin Pt/Co/Pt trilayer, from the perpendicular to in-plane direction, via graded Ar+ irradiation. In regions exhibiting perpendicular anisotropy, the power spectrum of the magnetization noise, S(ν), exhibits a remarkably robust ν-3/2 power law over frequencies ν from 1 kHz to 1 MHz. As the SRT region is traversed, however, S(ν) spectra develop a steadily-increasing critical frequency, ν0, below which the noise power is spectrally flat, indicating an evolving

SUBMITTER: Balk AL 

PROVIDER: S-EPMC6459195 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature