Induced antiferromagnetism and large magnetoresistance in RuSr2(Nd,Y,Ce)2Cu2O10-d ruthenocuprates

RuSr2(Nd,Y,Ce)2Cu2O10-d ruthenocuprates have been studied by neutron diffraction, and magnetotransport and magnetization measurements, and the electronic phase diagram is reported. Separate Ru and Cu spin ordering transitions are observed, with spontaneous Cu antiferromagnetic order for low hole-doping levels p, and a distinct, induced-antiferromagnetic Cu spin phase in the 0.02<p<0.06 pseudogap region. This ordering gives rise to large negative magnetoresistances which vary systematically with p in the RuSr2Nd1.8-xY0.2CexCu2O10-d series. A collapse of the magnetoresistance and magnetization in the presuperconducting region may signify the onset of superconducting fluctuations.