科研之友
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摘要
The magnetic properties of cobalt-based oxypnictides SmCoAsO are investigated by measuring magnetization, magnetoresistance and specific heat. The compound undergoes a ferromagnetic (FM) transition around T-c of 80 K, and a ferromagnetic to antiferromagnetic (AFM) transition below T-N1 of about 45 K, and finally an AFM order of Sm ion at T-N2 of 5.6 K. The weak FM order should originate from the itinerant 3d electrons of Co ions in the CoAs layers. We propose that the magnetic structure should be A-type AFM, which means that the FM order remains within the CoAs layer and the magnetic coupling between the CoAs layers becomes AFM below T-N1 of 45 K. The AFM coupling between the CoAs layers should be very weak. A magnetic field mu H-0 of about 2 T may cause an AFM-FM metamagnetic transition. A rich magnetic phase diagram is established and the interplay between the 3d electrons of Co ions and 4f electrons of Sm ions is discussed.
