[1] Univ Cambridge, Cavendish Lab, JJ Thomson Ave, Cambridge CB3 0HE, England
[2] Lawrence Berkeley Natl Lab, Div Mat Sci, Berkeley, CA 94720 USA
[3] Univ Grenoble Alpes, CNRS, CEA, Grenoble INP,INAC,SPINTEC, F-38000 Grenoble, France
[4] Univ Strasbourg, CNRS, Inst Phys & Chim Mat Strasbourg, UMR 7504,Dept Magnet Objects Nanoscale, F-67000 Strasbourg, France
[5] UC Santa Cruz, Dept Phys, Santa Cruz, CA 95064 USA