MAGNETIC-NONMAGNETIC TRANSITION IN CRAS AND THE RELATED-COMPOUNDS

Crystallographic parameters of Cr1-xMxAs (M=Ti, Mn, Fe, Co, and Ni; x less-than-or-equal-to 0.1) and CrAs1-xXx (X=P and Sb; x less-than-or-equal-to 0.1) have been precisely determined as a function of temperature from 77 to 320 K. Discontinuous changes of lattice parameters have been observed at the Neel temperature. By this crystallographic method, the Neel temperatures T(N) of these systems have been determined. By analyzing the results, it has been found that the magnetic state of the compounds around CrAs is strongly controlled by orthorhombic B-axis length: (i) the compounds with B axis less than a critical length B(c) of 3.38 angstrom do not have magnetic ordering and are Pauli paramagnetic down to 0 K: (ii) the compounds with B axis greater-than-or-equal-to B(c) undergo a transition at T(N) from helical to Pauli paramagnetic states: (iii) the compounds of NiAs type with larger B axis (hexagonal a axis) show a Curie-Weiss paramagnetism at high temperatures.