Pyung Woo Jang

Effects of annealing condition on the structural and magnetic properties of FePt thin films

Equiatomic FePt films were deposited by a dc sputtering method and annealed in the air and in a vacuum at 350/spl deg/C for up to 60 min. The order-disorder transformation occurs almost entirely within 10 min and a very high coercivity of 6.8 kOe could be obtained in the air-annealed films while the transformation occured very slowly in the vacuum-annealed films. This higher transformation rate could be also verified in the X-ray diffraction analysis. The reason for the higher rate seems to be the diffusion of oxygen atoms and possible mechanism was discussed.

New growth method of solid phase epitaxy in sputtered YIG films

A new method of growing YIG films by solid phase epitaxy was attempted, for which amorphous Y-Fe-O films were sputtered on GGG [111] substrates at room temperature with a high sputtering rate, and subsequently annealed in various atmosphere at a temperature higher than 650/spl deg/C. A possibility for SPE in YIG film could be verified by a constant growth rate of YIG films during the annealing as well as by results of both /spl theta/-2/spl theta/ scanning and a very low value of /spl Delta//spl theta//sub 50/ in rocking curves.

Magnetic properties of (Co/sub 93/Cr/sub 7/)-P-Pt/Cr thin films for longitudinal magnetic recording media

We report here (Co/sub 93/Cr/sub 7/)-P-Pt thin films with coercivity higher than 2600 Oe at the thickness of 180 /spl Aring/ (M/sub r//spl middot/t value of 0.9 memu/cm/sup 2/) even when they were deposited without substrate heating and bias voltage. The effects of the film composition and the magnetic layer thickness were studied. The coercivity of Co-Cr-Pt film increased with addition of P up to 12 at.%. With addition of P, the degree of Co (0002) texture was reduced and the grain size of films became more uniform. These effects appear to be associated with the coercivity increase. >

Heat treatment effects of CoCr sputtered films

Thermomagnetic analyses of RF-sputtered Co/sub 84/Cr/sub 16/ and Co/sub 78/Cr/sub 22/ thin films are reported. It is found that, when CoCr film is heated lower than the HCP to FCC transformation temperature, M/sub s/ drops substantially after holding at a constant temperature, and M/sub s/ at room temperature decreases after one cycle of heat treatment. This is due to Cr redistribution from the Cr-rich region of the film. When CoCr is heated higher than the HCP to FCC transformation temperature, M/sub s/ jumps sharply after holding at a constant temperature. This is due to the formation of an FCC phase with high M/sub s/ at higher temperature. A study of the angular dependence of coercivity indicates that the demagnetization mechanism of as-sputtered film seems to be an incoherent rotation mechanism while for the heat-treated film it may be domain wall motion or another combined mechanism. The perpendicular anisotropy in the Cr film may be connected with the existence of a highly Cr segregated region as well as c-axis alignments. >

High coercivity and small grains of Fe/sub 60-x/Pt/sub 40/Cu/sub x/ ternary thin films

Summary form only given. L1/sub 0/ FePt thin films with high coercivity and remanence are generally considered a good potential material for use as a high density recording medium. The medium also requires isolated small particles to reduce inter-grain magnetic interactions, which leads to lower noise. Many third metallic elements such as Cr, Ti, W, and etc were added to achieve these goals. However, decrease of coercivity was unavoidable in these metallic films. In this paper we first report a high coercivity as well as smaller grains of Fe/sub 60-x/Pt/sub 40/Cu/sub x/ ternary thin films. Coercivity higher than 10 kOe and small grains of 30 nm could be achieved when 4 at. % Cu were added in 50 nm Fe/sub 60/Pt/sub 40/ films. For these, 50 nm Fe/sub 60-x/Pt/sub 40/M/sub x/ (M=Cu, Cr) thin films were sputtered from Fe-Pt-(Cu, Cr) composite target on the coming 7059 glass by DC magnetron sputtering.

Structural and magnetic properties of Fe films epitaxial grown on Pd[100]/Cu[100]/Si[100] by sputtering

Epitaxial growth on the hydrogen terminated Si substrates is very interesting from the view point of application as well a s hasic research. To decrease mismatch between metals and Si substrates, several metallic films have been grown as a seed laydl-31. To do this work. an e-beam evaporation or a molecular beam epitaxy (MBE) were used. Fe(100) films on Pd(100)/Cu(100)/Si(lM)) were epitaxially grown by the very common process of an rf magnetron sputtering. in order lo investigate the dependence of the structural and magnetic properties on the film thickness.

Structural and magnetic properties of Fe films epitaxially grown on Pd[001]/Cu[001]/Si[001] by sputtering

5-150 nm Fe[001]/70 nm Pd[001]/85 nm Cu [001] films were epitaxially grown on Si[001] by RF sputtering. Magnetic and structural properties were analyzed by VSM, torque magnetometer and X-ray diffractometer. Epitaxial relationship of Fe[001][110]/spl par/Pd[001][010]/spl par/Cu[001][010]/spl par/Si[001][110] was confirmed. The hysteresis loops were characteristic of biaxial anisotropy and the anisotropy fields estimated from magnetization curves were in good agreement with the torque data. Uniaxial anisotropy was mixed with biaxial anisotropy in the torque data. Biaxial crystalline anisotropy decreased with decreasing film thickness while uniaxial anisotropy increased. With decreasing film thickness, the direction of uniaxial anisotropy was changed from [100] axis to [110] axis. The origin for the uniaxial anisotropy was the orthorhombic deformation of Fe layer which was more pronounced in thinner films.