Scripta hfateriah, Vol. 34, No. 9, pp. 1393-1398,1996 Elsevia Science Ltd PI1 31359-6462(96)00010-3 Copyright 8 1996 Acta Metellurgica Inc. Printed in the USA. All rights nscrwd 1359-6462/96 $12.00 + .OO ATOMIC AND MAGNETIC SHORT-RANGE ORDER IN h-17 at.% Mn H. Roelofs’, B. Schiinfeld’, G. Kostorz’, W. Biihre?, J.L. Robertson3, P. Zschack4, and G.E. Ice4 ‘Institut fIir Angewandte Physik, Eidgenbssische Technische Hochschule Zurich, CH-8093 Zurich, Switzerland. *Laboratorium fIir Neutronenstreuung der Eidgenbssischen Technischen Hochschule Zurich, c/o Paul Scherrer Institut, CH-5303 Wiirenlingen, Switzerland ‘Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN 3783 l-6118, USA. 4Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6118, USA. (Received October 20, 1995) Introduction In noble-metal alloys, diffuse peaks have often been observed at 1 l/2 f 6 0 positions in diffuse neutron or X-ray scattering experiments. These peaks are connected with the presence of flat regions of the Fermi surface and are called 2kr peaks. They were found in the magnetic scattering of Q@In [l] and &-Mn [2] as well as in the chemical, i.e. non-magnetic scattering of Q-Al [3], a-Zn [4], Q-Pd [5], &-Mn [2] and &-Mn [6]. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA These peaks in the magnetic scattering are usually attributed to strongly damped antiferromagnetic spin density waves I@DW) in a matrix with ferromagnetic character [I]. The origin of the SDW lies in the magnetic polarization of the electron gas, which cannot be detected directly in scattering experiments, since the wave faction of the conduction electrons is extended and thus their form factor differs from zero only at very small values of ]hj (h is the scattering vector in units of 2&, a = lattice parameter) [7]. The spins of solute atoms carrying a magnetic moment, such as Mn embedded in a copper matrix, sensitively follow the local magnetization of the electron gas. Thus, the SDW can be indirectly observed in the difise magnetic scattering serving actually as a probe of the Mn spins. In analogy the charge polarization of the electron gas is observable in the 2k, peaks of the chemical short-range order scattering. Local atomic arrangements based on the L12 structure with built-in antiphase boundaries along (100) planes are found to be typical for these alloys (see [3] and references therein). Antiferromagnetic ordering caused by a static SDW in the conduction electron gas of an alloy with dilute paramagnetic solutes, has been treated by Overhauser [S]. In alloys showing magnetic as well as chemical 2k, peaks, it is important to examine any correlations between charge density waves (CDW) and SDW, or more precisely, the corresponding atomic and spin arrangements. Recently Koga et al. [2] investigated a ,4g-20.8 at.% Mn single crystal quenched from 1123 K. A preferred occupation of like atoms at interatlomic distances Imn = 200, 400 etc. (the indices Imn refer to distances in units of u/2) is 1393