TEMPERATURE-DEPENDENCE OF ESR ABSORPTION INTENSITY OF ULTRAFINE ZN AND MG PARTICLES

Recently reported temperature dependence of spin susceptibilities of ultrafine particles (UFP's) of Zn and Mg exhibiting Curie-like behavior is found not to originate from the quantum size effect of conduction electrons but from an impurity effect. The microwave power saturation, especially enhanced in the smaller UFP's, suppresses the ESR intensity at low temperature and gives a complicated temperature dependence. ESR signal from the conduction electrons (CESR) cannot be detected in Zn UFP's, but observed in Mg UFP's with very broad linewidth. These phenomena are explained in relation to the size and shape effects of UFP's combining with the nature of CESR observed in bulk for both metals. © 1990.