Soft Magnetism and Morphology of Fe Films by Dual Ion Beam Sputtering
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SOFT
MAGNETISM AND MORPHOLOGY OF Fe FILMS BY DUAL ION BEAM SPUTTERING
M. Nagakubo, T. Yamamoto, and M. Naoe Dept. of Physical Electronics, Tokyo O-okayama, Meguro-ku, Tokyo 152, Japan.
Institute
of
Technology,
2-12-1,
ABSTRACT Fe films have been deposited by using dual ion beam sputtering apparatus under various conditions, and the dependence of their magnetic properties and morphology on preparation parameters such as film thickness, 6t, and argon gas pressure, P r, have been investigated in detail. The saturation magnetiza ion 4TrMs of the specimen films did not change remarkably with 6t in the range of 50 -10O0nm. However, with decrease of 6t below 50 nm, 4rrMs decreased to less than 20 kG and coercivity Hc increased to more than 16 Oe. As P increased from 0.5 to 1.6 mTorr without ion bombardment, 4TrMs decreasM to less than 20 kG and Hc increased to about 20 Oe. The SEM micrographs of these films deposited at higher PA showed the columnar structure. On the other hand, the films deposited at Yower PAr and ones bombarded by argon ions with proper kinetic energy during deposition did not present any texture and exhibited better soft magnetism. Such a morphology may be attributed to the difference in arrival energy of sputtered Fe particles to film surface and related closely to soft magnetism. It has been found that the dual ion beam sputtering method can control 4irMs and Hc with changing PAr and so prepare Fe films with superior soft magnetism by adjusting the kinetic energy of bombarding argon ions at lower PAr"
INTRODUCTION Recently, the ultra-high purity Fe has become of major interest for the revivified ferromagnetic materials. Especially, Fe films with soft magnetism may be useful for a thin film type of magnetic head. However, the magnetic properties of Fe films are not always the same as bulk Fe because they are affected by the preparation process and the presence of impurities in films. Effects of gas addition by ion bombardment of the surface layers of growing films have been already reported.[1] In a previous study, it was verified that the bombardment of argon and hydrogen ions accelerated at a voltage of 500 V and current density of about 20 WA/cm during deposition improved the soft magnetism of Fe films, resulting from enhancing the microscopic uniformity and atomic ordering in Fe films. The influence of film thickness 6t and working gas pressure, P Ar' on magnetic properties is important from the viewpoint of practical application. Dual ion beam sputtering method is very useful for studying growth uniformity and film morphology because of good controllability of deposition parameters such as P Ar and ion acceleration voltage. In addition, the bombardment of argon ions with proper kinetic energy onto growing surface layer may change the film structure drastically and directly. In this study, the 6t and PAr dependences on magnetic properties and morphology of Fe films have been investigated, and the effects of ion bombardment to growing surface layer on them have been examined.
Mat. Res. Soc
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