Phys. rev. mater. Phys. rev. mater. Ultrathin bismuth-yttrium iron garnet films with tunable magnetic anisotropy Wang Hanchen Legrand William Petrosyan Davit Kang Min-Gu Karadža Emir Matsumoto Hiroki Schlitz Richard Lammel Michaela Aguirre Myriam H. Universidad de Zaragoza Gambardella Pietro 2026 research-article