SIPS 2018

DETAILLED PROGRAM OVERVIEW

Cobalt Ferrite — New Aspects in Magnetization Behaviour
Reiko Sato¹;
¹TECHNICAL UNIVERSITY OV VIENNA, INSTITUTE OF SOLID STATE PHYSICS, Vienna, Austria;
PAPER: 264/SISAM/Invited (Oral)
SCHEDULED: 16:45/Wed./Copacabana A (150/1st)

ABSTRACT:
Recently, CoFe2O4 is of more physical and technological interest, because among the ferrites, it exhibits the highest magnetocrystalline anisotropy as well as a high magnetostriction (100=590 ppm), high strain sensitivity (one order larger than that of polycrystalline terfenol (λs = 1000 ppm)), and low raw material costs, whose properties are appropriated for non-contact sensor and sonar detection field. Additionally, CoFe2O4 is an insulator that is one of the few materials which can be used for bulk magnetoelectric composites. The grain size, magnetic properties, and cations distributions in octahedral and tetrahedral sites depend strongly on the production method. With forced hydrolysis method, a grain size of 3 nm could be achieved [1], which is very important for biomedical applications. Pressing ball milled cobalt ferrites under high pressure and sintering in a high external field can obtain a magnetostriction up to 400 ppm [2]. Low temperature magnetization measurements on single crystalline Co0.8Fe2.2O4 gave evidence of a first order magnetic process (FOMP) transition, which occurs when applying the external field in the [111] direction [3]. This transition is also well visible in the magnetostriction data. Such transition gives evidence of two competing anisotropy directions or two no equivalent magnetization sites, which may be due to different valent states at 3d atoms. Due to the complex preparation methods of single crystal cobalt ferrite, more attention has been given on polycrystalline cobalt ferrites to obtain high magnetostriction. In this work, special emphasis will be given on the temperature dependence of enhanced magnetostriction of CoFe2O4 by annealing the sample (produced by ball milling and sintered at 1000°C for 12 h) with strong magnetic field of 10 T, at 300 °C for 3 h and cooling down to room temperature with the presence of field. These results will be compared with those data obtained for the sample before the magnetic field annealing.

References:
[1] Giap V. Duong, R. Sato Turtelli, N. Hanh, D.V. Linh, M. Reissner, H. Michor, J. Fidler, G. Wiesinger, R. Grössinger, J. Magn. Magn. Mater. 307 (2006) 313-317.
[2] Atif Muhammad, Reiko Sato-Turtelli, Martin Kriegisch, Roland Grössinger, Frank Kubel, and Thomas Konegger, Journal of Applied Physics 111, 013918 (2012).
[3] Martin Kriegisch, Weijun Ren, Reiko Sato-Turtelli, Herbert Müller, Roland Grössinger, and Zhidong Zhang, Journal of Applied Physics 111, 07E308 (2012).