Abstract
We report here the results of Debye-Scherrer X-ray diffraction measurements in the temperature range from 12K to 300K of the perovskite compounds SrRuO3 and CaRuO3. We show that SrRuO3 indicates an clear anomaly with the temperature dependence of the unit-cell parameters and volume below its ferromagnetic transition temperature Tc of 160K through magnetovolume effect. In particular, the volume of SrRuO3 is almost constant below Tc, and invar effect is discovered for the first time in transition-metal oxide, which is seen in 3d transition-metal itinerant magnets, e.g., Fe-Ni alloy. Therefore, it is concluded that SrRuO3 is classified to a moderately weak itinerant ferromagnet. On the other hand, CaRuO3 shows no anomaly in the variation of the volume with temperature, suggesting that magnetic ordering does not occur in this compound.
