Ž . Thin Solid Films 372 2000 218222 Magnetoresistance and spin fluctuation resistivity of -Mn thin films and their relationship to substrate temperatures F. Boakye a,  , R.K. Nkum a , K.G. Adanu b a Department of Physics, Uni  ersity of Science and Technology, Uni  ersity Post Office, Kumasi, Ghana b Department of Physics, Uni  ersity of Ghana, Legon, Ghana Received 10 October 1999; received in revised form 4 March 2000; accepted 19 May 2000 Abstract Electrical resistivity measurements in thermally evaporated -Mn thin films have been carried out between 10 and 1.4 K using the van der Pauw four probe technique in magnetic fields up to 9 T. The results reveal a wide variation of the anomalous coefficient of T 2 at low temperatures. This variation is found to be influenced by substrate temperatures. At high substrate Ž . Ž . temperatures 300°C a film whose residual resistivity in the expected range 0.10 0.85  m of bulk -Mn is formed and its anomalously large coefficient of T 2 at low temperatures is found to decrease appreciably with magnetic field. The magnitude of the resistivity at such low temperatures does not change for films coated on substrates held below 200°C in fields up to 9 T. In 2 2 Ž . such films the coefficient of T is negative and the magnitude of the coefficient of T , A increases with decreasing substrate temperatures.  2000 Elsevier Science S.A. All rights reserved. Keywords: Manganese; Magnetic moment; Spin fluctuations; Resistivity 1. Introduction Manganese is one of the strangest of the metallic conducting elements. Not only does it have four crystal-  lographic phase changes 1 as it cools from the liquid phase with an additional paramagnetic  antiferromag- netic phase transition at 95 K in the stable low temper- ature -Mn phase but in that additional phase, it has  one of the most complex crystal structures 2 of the elements with 58 atoms in a body centered cubic struc- ˚ ture of lattice constant 8.91 A and 29 atoms in a unit cell. This complicated crystal structure leads to four Ž. different atomic configurations in the unit cell: site i with a coordination number of 16 and one site per unit Ž. cell; site ii with a coordination number of 16 and four  Corresponding author. Tel.: 233-51-60299; fax: 233-51-60299. Ž . E-mail address: fboakye@avuust.africaonline.com.gh F. Boakye . Ž . sites per unit cell; site iii with a coordination number Ž . of 13 and 12 sites per unit cell; and site iv with a coordination number of 12 and 12 sites per unit cell.  Yamada et al. 3 in their neutron diffraction studies have described the magnetic structure of -Mn by a localized moment model with a single non-collinear Ž . configuration and the moment at sites i  iv have been found to be 1.9, 1.7, 0.6 and 0.25  , respectively, at 4.4 B K. In essence, as the packing around a particular ion gets closer, so the magnetic moment is reduced practi- cally to zero for a change of inter-ionic spacing from ˚ 2.96 to 2.21 A. It appears that the manganese ions exist in different electronic configuration depending on the degree of overlap with neighbouring ions. Although the Ž. Ž. large magnetic moment on site i and ii perseveres at  temperatures above the Neel point 4 , high resolution ´  X-ray photoemission spectroscopy 5 indicates that the Ž . Ž . moment on site iii and iv fluctuate rapidly since the multiplet splitting of the 3s and 2s lines shows a local- 0040-609000$ - see front matter  2000 Elsevier Science S.A. All rights reserved. Ž . PII: S 0 0 4 0 - 6 0 9 0 00 01038-5