1. Institute of Physics for Advanced Materials, Nanotechnology and Photonics (IFIMUP), Departamento de Física e Astronomia, Universidade do Porto, Porto 4169-007, Portugal
2. Departamento de Física de Materiales, Universidad del País Vasco, San Sebastián 20018, Spain
3. IKERBASQUE, the Basque Foundation for Science, Bilbao 48013, Spain
4. Institute of Magnetism NAS of Ukraine and MES of Ukraine, Kyiv 03142, Ukraine
5. Information Storage Materials Laboratory, Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576, Singapore