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.