[1] Arizona State Univ, Sch Elect Comp & Energy Engn, Tempe, AZ 85287 USA
[2] Lanzhou Univ, Sch Phys Sci & Technol, Lanzhou 730000, Gansu, Peoples R China
[3] Lanzhou Univ, Key Lab Magnetism & Magnet Mat MOE, Lanzhou 730000, Gansu, Peoples R China
[4] Univ Aberdeen, Inst Complex Syst & Math Biol, Kings Coll, Aberdeen AB24 3UE, Scotland