Reversible Magnetostriction with Temperature in Single Crystal Tb$_{5}$Si$_{2.2}$Ge$_{1.8}$

The magnetostriction changes that accompany the phase transitions of single crystal Tb$_{5}$(Si$_{2.2}$Ge$_{1.8})$ have been investigated at temperatures between 20 K and 150 K, by measurements of the reversible component of the magnetostriction along the crystallographic ``a'' axis. Over this temperature range the shape and slope of the magnetostriction curves change, which are indicative of changes in the magnetic state, crystal structure and magnetic anisotropy. Results show a phase transition that occurs near 106 K (onset-completion range 100 - 116 K). The abrupt nature of the strain transition, its unusual hysteresis, and its temperature dependence appear to indicate a first order phase transition which can be activated by applied magnetic field or temperature. Magnetostriction measurements at temperatures below the transition region show a magnetostriction of small overall magnitude but with a high, temperature dependent anisotropy. Funded by USDoE-Office of Basic Energy Sciences