Journal of Optoelectronics and Advanced Materials Vol. 5, No. 1, March 2003, p. 217 - 226 INVITED PAPER EASY AXIS DISTRIBUTION IN MODERN NANOPARTICLE STORAGE MEDIA: A NEW METHODOLOGICAL APPROACH V. Kuncser * , W. Keune a , M. Vopsaroiu b , P. R. Bissell b , B. Sahoo a , G. Filoti National Institute for Materials Physics, PO Box MG 7, 76900 - Bucharest-Magurele, Romania a Laboratorium für Angewandte Physik, Gerhard-Mercator-Universität, 47048, Duisburg, Germany b University of Central Lancashire, Magnetic Materials Research, Preston, PR1 2HE, UK Easy axis distribution in metal particle magnetic tapes for linear digital data storage were studied by Mössbauer spectroscopy and magnetometry, for comparison. Qualitative and quantitative agreement between the distribution parameters deduced at room temperature via the two different techniques was found. The proposed methodology based on the interpretation of the Mössbauer data has the advantage that it can be applied at different temperatures and for very thin films. Moreover, angular spin distribution at low temperatures were obtained by Mössbauer spectroscopy and discussed with respect to the room temperature results. There was evidenced that the room temperature easy axis angular distribution contains both static orientation and dynamical components. (Received July 20, 2002; accepted after revision March 12, 2003) Keywords: Metal particle magnetic tapes, Easy axis distribution, Mössbauer spectroscopy, Magnetometry 1. Introduction A special class of magnetic information storage media, namely the particulate media, has shown a continuously growing interest, due to a very basic recording principle and very low costs. When data density requirements were increased, the metal particle (MP) have replaced the oxide particle based storage media, imposing the advantage of higher saturation magnetisation for lower particle dimension [1]. Among them, elongated iron based metal particles provide large remanent magnetisation and coercivity. Such particles have to be stabilized against atmospheric oxidation by a careful passivation and various protective coatings. Unfortunately, even a passivation layer of a few nanometers can reduce the average magnetisation of the particles to one half of the bulk values. Even under these conditions, the MP systems present still superior performances compared with the iron oxide or cobalt-modified oxide particle systems [2,3]. Advanced MP tapes are now manufactured using double coating technologies which involve usually a thin magnetic layer superposed on a non-magnetic undercoat [1]. A magnetic field is applied during the polymer drying process, in order to increase the alignment of the particle easy axis, with large benefit to the storage performances. Increasing the magnetic texture, the squareness of the hysteresis loop becomes higher and the switching field distribution becomes narrower. In turn, the degree of magnetic texturing is very dependent on the technological procedures, e.g. the polymer viscosity, the rate of drying or the magnitude of the magnetic field. Therefore, the mapping of the easy axis distribution (EAD) in such materials is an important task devoted to the control of the manufacturing achievements. The degree of magnetic texture is described by a three-dimensional distribution. Due to the preparation conditions and the geometry of the system, a much narrower out-of-plane angular * Corresponding author: kuncser@alpha2.infim.ro