A μSR study of the magnetoresistive ruthenocuprates RuSr₂Nd_1.8−xY_0.2Ce_xCu₂O_10−δ(x= 0.95 and 0.80)

Abstract

Zero field muon spin relaxation (ZF-μSR) has been used to study the magnetic properties of the underdoped giant magnetoresistive ruthenocuprates (GMR) RuSr 2 Nd 1.8-x Y 0.2 Ce x Cu 2 O 10- (x = 0.95, 0.80). The results show a gradual loss of initial asymmetry A 0 at the ruthenium spin transition temperature, T Ru . At the same time the electronic relaxation rate,  shows a gradual increase with decreasing temperature below T Ru . These results have been interpreted as evidence for Cu spin cluster formation below T Ru . These magnetically ordered clusters grow as the temperature is decreased thus causing the initial asymmetry to decrease slowly. GMR is observed over a wide temperature range in the materials studied and the magnitude increases as the temperature is reduced from T Ru to 4 K which suggests a relation between Cu spin cluster size and -MR.