High Spin-Low Spin Transition in MnAs1-xPx(x=0.075)

Some of the physical properties of the compound MnAs 1- x P x ( x =0.075) are investigated by the various measurements, and they can be divided into four different temperature ranges. The compound is: i) for T > T 2 , a high spin state paramagnet with the NiAs type ( B 8 1 ), ii) for T 1 < T < T 2 , a high spin state paramagnet with the MnP type ( B 31), iii) for T N < T < T 1 , an intermediate spin state paramagnet with the MnP type and iv) for T < T N , a low spin state antiferromagnet with the MnP type. Especially in the region iii), an interesting phenomenon of a high spin-low spin transition is observed, and characterized by a large change in the lattice constants and the electrical resistivity.