29, NO. 6, NOVEMBER 1993. Magnetostriction of Sputtered Sm-Fe Thin Films. T. Honda. Sendai Research Laboratory, Tokin Corporation, Sendai 982, Japan.
IEEE TRANSACTIONSON MAG"ICS,
3126
VOL.29, NO.6, NOVEMBER 1993
Magnetostriction of Sputtered Sm-Fe Thin Films T. Honda Sendai Research Laboratory, Tokin Corporation, Sendai 982, Japan
Y.Hayashi, K. I. Arai, K Ishiyama and M. Yamaguchi Research Institute of Electrical Communication,Tohoku University, Sendai 980, Japan A h u c f - The magnetostriction and the magnetic properties of amorphous SqFe-, thin Elms prepared by sputtering were investigated at room temperature. The magoetostrietion, -5 of these films increased rapidly in low fields (25kOe) to saturate the magnetostriction. Such hard magnetic characteristics do not match electromagnetic devices. On the other hand, many papers have reported that amorphous RE-TM alloys can be fabricated by rapid quenching techniques such as melt spinning, sputtering and evaporation [l].These amorphous alloys, having no magnetocrystalline anisotropies, are expected to exhibit soft magnetic properties, compared with crystalline RE-TM alloys. If amorphous RETM alloys have large magnetostriction and low saturation field, they would be useful for electromagnetic devices. However, only few systematic investigations have been carried out so far for the magnetostriction of amorphous RETMthinfilms. . Besides, Sm-Fe alloys have negative large magnetostriction as compared with other RE-TM alloys [l]. In particular thin films of this alloy would play an important role for development of new micro-actuators and sensors. In this study, we examined the magnetostriction and the magnetic properties of amorphous Sm-Fe system thin films as a function of the composition and the sputtering conditions (input power, Argas pressure and substrate temperature.) On the basis of these results, we discussed their possibility for magnetic micro-devices.
11. EXPERIMENTAL
Sm,Fe,,-, (5=3--54at%) thin films were prepared by rf magnetron sputtering. The target used was composed of a pure Fe plate (3inch$) and small Sm chips. After the chamber was pumped down to a pressure below 2 ~ 1 0 - ~ T o rthe r, films were deposited to a thickness of l p m on glass substrates with a thickness of either lmm or 0.15". During sputtering the substrate holder was water-cooled or heated up to 300°C. The range of rf input power was from 100 to 200W and the AI gas pressure was varied from 4 to 40mTorr. The coercive force, Hc, and the magnetization were measured using a vibrating sample magnetometer (VSM) in magnetic fields up to 18kOe. The intrinsic perpendicular uniaxial magnetic anisotropy, K,, was measured by means of a torque method. The magnetostriction was determined from the Curvature of the cantilevered substrate with a thickness of 0.15" in rotating in-plane fields [2][3]. This curvature was measured using a three-terminal capacitance bridge, in which the curvature was measured as a change in capacitance between the film and the fixed electrode. The film composition was determined using an electron probe microanalysis (EPMA). The film structure was analyzed using an X-ray diffractometer (XRD) with Co-ka X-ray. All measurements were carried out at room temperature.
A. Compositional Dependence Firstly, we examined the structure of Sm,Fe,,-, thin films deposited on the water-cooled substrates as a function of the Sm content. No obvious X-ray diffraction peaks were found between x=12 and 54. Therefore these films are amorphous material. When x
