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AM: Magnetismus

AM 2: Magnetische Phasenüberg
änge, Elektronentheorie

AM 2.3: Vortrag

Montag, 26. März 2001, 10:45–11:00, S 5.4

First-order high- to low-moment phase transition in FeNi alloys? — •H. Meinert¹, A. Perez¹, R. Schellenberg², and E. Kisker¹ — ¹Institut für Angewandte Physik, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf — ²Vacuumschmelze GmbH, 63450 Hanau

We have performed No-dqmagneticNo-dq core-level XPS as a function of the alloy composition in γ−Ni_xFe_1−x alloys, 0≤ x≤1, grown in-situ in ultra high vacuum on a Cu(001) substrate. The Fe and the Ni 2p_3/2 core level line intensity asymmetries occurring upon magnetization reversal are evaluated as functions of the composition. The concentration-weighted sum of the Fe and Ni asymmetries (CWAS), each of them considered to be proportional to the local magnetic moments, follows roughly that of the average moment determined by neutron scattering /1/. However, the drop of the CWAS data at the Invar composition (Ni₃₅Fe₆₅) is steeper than in the neutron scattering data. This sheds new light on the long-standing discrepancy between theories and the neutron scattering results, the theories predicting a sharp transition of first order /2,3/ whereas the neutron scattering data show a gradual collapse of the moment. The present measurements have been performed at room temperature. Lower-temperature measurements are in preparation to check for a further sharpening of the transition.

Supported by the DFG and by the MSWWF, NRW.

1. for a compilation of Neutron scattering data see V.L. Sedov et al., J.M.M. 183, 117 (1998); 2. M. Schröter et al., Phys. Rev. B52, 188 (1995; 3. I. A. Abrikosov et al., Phys. Rev. B 51, 1058 (1995)