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The Gaussian spin fluctuation theory is applied to study magnetic properties (Curie temperature, magnetization) of EuO ultra-thin films within nearest neighbor and next nearest neighbor exchange approximation. The dependence of Curie temperature on the thickness of the free EuO ultrathin film is calculated and compared with the results of the other mean field methodconstant coupling approximation. The effect of nearly independence of saturation magnetization on the EuO films thickness measured in [8] can be explained by controlling the next nearest neighbor exchange in presence of substrates. | Communications in Physics, Vol. 23, No. 3 (2013), pp. 235-240 INFLUENCE OF SPIN FLUCTUATION ON THE MAGNETIC PROPERTIES OF EUO ULTRA-THIN FILM PHAM HUONG THAO Faculty of Physics, Hue College of Education, 32 Le Loi, Thua Thien Hue,Vietnam BACH THANH CONG Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan Hanoi,Vietnam Email: congbachthanh@gmail.com Received 25 June 2013 Accepted for publication 15 September 2013 Abstract. The Gaussian spin fluctuation theory is applied to study magnetic properties (Curie temperature, magnetization) of EuO ultra-thin films within nearest neighbor and next nearest neighbor exchange approximation. The dependence of Curie temperature on the thickness of the free EuO ultrathin film is calculated and compared with the results of the other mean field methodconstant coupling approximation. The effect of nearly independence of saturation magnetization on the EuO films thickness measured in [8] can be explained by controlling the next nearest neighbor exchange in presence of substrates. I. INTRODUCTION In the recent years, magnetic properties of thin films which have been intensively investigated by both theoretical and experimental methods expose a great potential for applications [1]. The important reasons of magnetic size effects in the thin films, such as the reduction of the Curie temperature TC , are the finite thickness and the broken translational symmetry along the direction perpendicular to the film surfaces. Many theoretical methods are used to study the magnetic properties of thin films such as, the standard mean field (MF) methods [2] including the Weiss mean field, the Oguchi’s cluster and the constant coupling approximations (CCA), spin wave method [3], and recently, the integral functional integral method [4]- [5]. Our paper is aimed to apply the Gaussian spin fluctuation (SF) theory developed by us [4] for a real spin system of EuO thin film. Here we consider the next nearest neighbor (NNN) exchange
