Eur. Phys. J. B 19, 425-431 (2001)
https://doi.org/10.1007/s100510170319

Anomalous magnetic field dependence of T_AF in La_0.95Sr_0.05MnO₃

¹ Experimentalphysik III, Institut für Physik, Universität Augsburg, 86159 Augsburg, Germany
² General Physics Institute of the Russian Acad. Sci., 117942 Moscow, Russia

Corresponding author: ^a dietrich.maurer@physik.uni-augsburg.de

Received: 27 March 2000
Published online: 15 February 2001

Abstract

The magneto-elastic properties of single-crystalline La_0.95Sr_0.05MnO₃ have been studied ultrasonically. Our investigations focussed on the temperature interval where magnetic ordering starts to evolve and results in a spin canted antiferromagnetic ground state. In detail the experiments revealed that the magnetic order parameter in low-doped manganite is only weakly coupled to lattice strains. Furthermore, the anomalous temperature dependence of the order parameter as found resembles highly that in stoichiometric LaMnO₃. However, the main and most surprising finding is that external magnetic fields favor the spin canted phase in La_0.95Sr_0.05MnO₃. It is unclear at present how the exchange interaction can be tuned by magnetic fields in the way observed and we are not aware of existing theoretical concepts which might give a plausible explanation for the unexpected field dependent behavior of the critical temperature. We believe, however, that this behavior primarily results from the fact that the exchange interaction depends sensitively on the orbital configuration of the manganese d electrons.