The effect of holmium doping on the magnetic and transport properties of

Abstract

We have studied the evolution of the transport and magnetic properties with holmium doping for . We observe a systematic decrease in the ferromagnetic transition temperature , the metal - insulator transition temperature and the rhombohedral cell volume with increasing holmium concentration. For the concentration with x = 0.4, we observe a metallic spin-glass phase with the spin-glass freezing temperature , and a large magnetoresistance ratio at low temperature, which indicates that a proportion of the spins are in a frustrated state. The high-field magnetization of the holmium-doped samples is much less than the magnetization that would be expected if the were in a ferromagnetic state, showing that there is substantial canting in the manganese lattice. We believe that the ferromagnetic component in the spin-glass phase for x = 0.4 crosses the percolation threshold, giving rise to metallicity in the sample.