Magnetic behavior of nanocrystalline ErCo(2).

We have investigated the magnetic behavior of the nanocrystalline form of a well-known Laves phase compound, ErCo(2)-the bulk form of which has been known to undergo an interesting first-order ferrimagnetic ordering near 32 K-synthesized by high-energy ball-milling. It is found that, in these nanocrystallites, Co exhibits ferromagnetic order at room temperature, as inferred from the magnetization data. However, the magnetic transition temperature for the Er sub-lattice remains essentially unaffected suggesting the (Er)4f-Co(3d) coupling is weak on Er magnetism. The net magnetic moment as measured at high fields, for example at 120 kOe, is significantly reduced with respect to that for the bulk in the ferrimagnetically ordered state and possible reasons are outlined for this. We have also compared the magnetocaloric behavior for the bulk and for nanoparticles.