Magnetostriction of Hexagonal HoMn[O.sub.3] and YMn[O.sub.3] Single Crystals

We report on the magnetostriction of hexagonal HoMn[O.sub.3] and YMn[O.sub.3] single crystals in a wide range of applied magnetic fields (up to H = 14 T) at all possible combinations of the mutual orientations of magnetic field H and magnetostriction [DELTA]L/L. The measured [DELTA]L/L(H, T) data agree well with the magnetic phase diagram of the HoMn[O.sub.3] single crystal reported previously by other authors. It is shown that the nonmonotonic behavior of magnetostriction of the HoMn[O.sub.3] crystal is caused by the [Ho.sup.3+] ion; the magnetic moment of the [Mn.sup.3+] ion parallel to the hexagonal crystal axis. The anomalies established from the magnetostriction measurements of HoMn[O.sub.3] are consistent with the phase diagram of these compounds. For the isostructural YMn[O.sub.3] single crystal with a nonmagnetic rare-earth ion, the [DELTA]L/L(H, T) dependences are described well by a conventional quadratic law in a wide temperature range (4- 100 K). In addition, the magnetostriction effect is qualitatively estimated with regard to the effect of the crystal electric field on the holmium ion.