科研之友
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摘要
CeAgAs2, an HfCuSi2 like layered pnictide, orders antiferromagnetically at T-N=6.2(1) K. The ordering process was monitored in neutron diffraction experiments in the temperature range 10 K %26gt;= T %26gt;= 3.5 K. At T=4 K the lattice parameters are a=5.7438(1) angstrom, b= 5.7696(1) angstrom and c=21.0067(2) angstrom. The diffraction pattern of the antiferromagnetic phase with a propagation vector k=[0,0,0] point towards ferromagnetically ordered moments in Ce layers stacked along [001], the individual layers are coupled antiferromagnetically with a + - - + type sequence. The alignment of moments within the Ce layers cannot be determined reliably from the experimental data so that two different structure models are discussed. The proposed metamagnetic transition was confirmed by diffraction experiments applying an external magnetic field at T %26lt; T-N. In the interval 4 K %26lt;= T %26lt;= 6 K, a relatively small field of mu H-0 approximate to 0.3 T suffices to fully suppress the antiferromagnetic ordering. The effect is completely reversible yet subject to hysteresis: After switching off the external field at any T %26lt; T-N the magnetic reflections gain their original intensity within several 10 min indicating the restoring of the antiferromagnetic phase.
- 出版日期2012-3
