Magnetostriction of rare earth double tungstates

The isothermal, longitudal and transverse magnetostriction of rare earth double tungstates KDy(WO4)(2), KHo(WO4)(2) and RbNd(WO4)(2) has been measured at low temperatures along the crystallographic axes in a magnetic field up to 12 T. The measurements have been performed by the strain gauge method on single crystals. For all three axes, we observed anomalies connected to the structural phase transitions induced by a collective Jahn - Teller effect or by strong external field at temperatures near a spontaneous structural phase transition of Jahn - Teller nature. It was shown that all the studied phase transitions are of first order. The magnetostriction measurements in rare earth double tungstates are important and interesting, since: (i) in these objects, there is a Jahn - Teller spontaneous structural transition at low temperatures; (ii) information on the behaviour of an elastic subsystem in these samples is necessary for understanding the mechanism of this transition under the influence of an external magnetic field applied along the crystallographic axes; (iii) it allows us to form a conclusion on the anisotropy of the studied phenomenon.