Spin Order in FeCr2O4 Observed by Mössbauer Spectroscopy

57Fe Mössbauer spectroscopy has been conducted on a single crystal FeCr2O4, in order to examine Fe2+ spin order. By adding a slight compression along the cubic 001 axis during cooling through the transition temperatures, single domain states of tetragonal and orthorhombic phases were attained. In the ferrimagnetic phase below 65K, the spins are in the c-plain of the orthorhombic phase and directed at about 45° from the a-axis. With decreasing temperature, the spins tend to rotate toward the a-axis. Below 35K in the spiral magnetic phase, the spins are directed in two directions in the c-plane; one is directed at about 60° from the a-axis, while the other is directed along the a-axis. This indicates that more complicated spin order than a simple cone conical structure is realized.