Low-temperature magnetism ofNd2CuO4: An ultrasonic investigation

Abstract

We have performed an ultrasonic study of Nd 2 CuO 4 in order to investigate the low temperature magnetism due to the Nd 3+ moments. In addition to small anomalies corresponding to the Cu 2+ spin reorientations observed at 33 and 67 K, a large magnetic field and frequency dependent anomaly is detected around 4 K in the C 66 elastic constant and the corresponding attenuation variations. The frequency dependence of this anomaly, which disappears under a magnetic field of 2 T applied along the in-plane Cu-O bonds, is related to a resonant phenomenon rather than to a phase transition as previously reported. The ultrasonic measurements suggest the development of local domains, due to a frustration of the magnetic structure caused by the competition between the Nd 3+ -Cu 2+ and the Nd 3+ -Nd 3+ interactions at low temperature. In contrast to the common belief, the C 66 elastic constant and attenuation anomalies above 2 T characterize a field-induced transition of the Nd 3+ spins which occurs at critical field lower than the one associated with the Cu 2+ spins.

Progress and perspectives on electron-doped cuprates

“…The reordering and the low temperature interaction of Nd with Cu can be observed in various other ways. The reorientations were first observed by muon spin resonance and rotation experiments (Luke et al, 1990) and were confirmed later on by crystal-field spectroscopy (Jandl et al, 1999), and more recently by ultrasound propagation experiments (Richard et al, 2005b). The growing competition between the three energy scales leads also to a wide variety of anomalies at low temperature (Cherny et al, 1992;Li et al, 2005a,b;Richard et al, 2005a,b;Wu et al, 2008).…”

Giant Anisotropy of Magnetoresistance and "Spin Valve" effect in Antiferromagnetic $Nd_{2-x}Ce_xCuO_{4}$

“…It is well known that the neighboring CuO 2 plane with antiferromagnetic configuration is separated by Nd-O layer. 15 As discussed above, the magnetic structure of Nd 3+ subsystem can be turned by external field. Therefore, the out-of-plane transport can be switched by magnetic field assuming the Nd-O layer as a barrier.…”

“…An enhancement of neutron scattering magnetic peak intensities around 3 K has been interpreted as Nd 3+ ordering due to Nd 3+ -Nd 3+ interaction 12 , while Lynn et al have estimated the Nd 3+ ordering temperature around 1.5 K 17 . Recently, an abnormal peak around 5 K observed in ultrasonic measurement is explained to be somehow related to local magnetic domains 15 . Since the Nd 3+ -Cu 2+ and Nd 3+ -Nd 3+ interactions are opposite, the former is dominated above 5 K and makes Nd 3+ parallel to Cu 2+ as shown in Fig.…”

“…The observed fourfold symmetry below 5K in magnetization could arise from the reorientation of Nd 3+ spin. Richard et al have given evidence that the magnetic structure below 5 K has anisotropic field-dependence 15 . As shown in Fig.…”

“…12 Magnetic structure of Nd 3+ is very abundant at low temperature. 14,15,16 In this sense, electronic transport at low temperature is expected to be sensitive for the change of magnetic structure of Nd 3+ due to strong spin-charge coupling. It will provide us a chance to understand the spin-charge coupling in electron-doped cuprates.…”