Search for orbital moments in underdoped cuprate metals

Polarized neutron-diffraction experiments have been performed in search of the orbital magnetic moments recently predicted in a theory for the cuprate metals. Both La2-xSrxCuO4 [LSCO(x)] and YBa2Cu3O6+x [YBCO(x)] compounds we re investigated. No definitive evidence for the existence of such a three-d imensionally ordered moment was found in any of these samples within experi mental uncertainty, which was as low as 0.01 mu(B). We have also investigat ed the possibility that a magnetic rod exists parallel to the c axis in the case of two- or quasi-two-dimensional ordering in the (a,b) plane and have set an upper limit for the total moment to be 0.1 mu(B) in LSCO (x = 0.1). [S0163-1829(99)02938-0].