Kibong Song

OCCURRENCE OF LARGE PERPENDICULAR MAGNETIC ANISOTROPY IN BILAYERED FILMS WITH NANOMETER-THICK TBFECO AND AL LAYERS

For Tb‐Fe‐Co(MO)/Al bilayered films, dependence of perpendicular magnetic anisotropy constant K u ⊥ on MO layer thickness t MO of 3–300 nm and Al layer thickness t Al of 5 and 100 nm has been investigated. For either t Al, easy magnetization direction was normal to film plane at t MO above 4 nm. K u ⊥ of films with t Al of 5 nm increased drastically with increasing t MO for t MO<10 nm and then assumed a constant value of 4×106 erg/cm3 which is two times larger than that with t Al of 100 nm. This difference in K u ⊥ between them may be attributed to stress induced anisotropy. Estimation of rotational hysteresis loss W r and its integral R suggests that the mechanism of magnetization reversal may be attributed to incoherent curling mode.

Microstructure and thermal stability of TbFeCo thin films prepared by plasma-free sputtering

Abstract Amorphous TbFeCo thin films prepared using the facing targets sputtering apparatus have been investigated. The specimen films deposited at an argon pressure PAr of 0.5 mTorr and a deposition rate Rd of 100 nm min−1 revealed a very smooth surface and a dense, uniform and columnless morphology, and had a thinner surface oxidation layer than the films deposited at a PAr of 7.5 mTorr and the same Rd. The films deposited at a PAr of 3.6 mTorr and Rd of100 nm min−1 also revealed a dense, uniform and columnless morphology, but the films deposited at the same PAr and a Rd of 50 nm min−1 presented a clear columnar microstructure. The films post-annealed at temperatures up to 220°C showed structural relaxation.

Improvement of magneto‐optical characteristics of TbFeCo/Al bilayered films at a short wavelength of 400 nm

Bilayered films composed of amorphous TbFeCo alloy and Al layers were deposited successively on glass slide substrates without plasma exposure using the facing targets sputtering system. The specimen films with the magneto‐optical (MO) layer thickness tMO of 14 nm have a Kerr rotation angle θK and figure of merit fM as large as about 0.36° and 0.25, respectively, at the wavelength λ as short as about 400 nm. These values of θK and fM are considerably larger than those of the bilayered films with larger tMO in the conventional MO media. Normally, the bilayered films with tMO above 50 nm have θK of about 0.25° and fM below 0.2 at λ of 400 nm.

Dependence of Kerr rotation angle of Tb-Fe-Co/Al bilayers on layer thickness

Amorphous Tb-Fe-Co/Al bilayers have been prepared by facing targets sputtering apparatus. The bilayers with ultra thin magnetooptic (MO) layers of 5 nm possessed magnetic anisotropy energy K/sub u/ as large as 1 approximately 2*10/sup 6/ erg/cm/sup 3/. Tb-Fe-Co(5 nm)/Al(5 nm) bilayers exhibited Kerr rotation angle theta /sub k/ as large as 0.58 degrees. >

Co-Cr/Al multilayers for perpendicular magnetic/magneto-optical two-way recording media

Co-Cr/Al multilayers exhibit excellent magneto-optical characteristics due to the well-defined interfaces between Co-Cr and Al layers. Consequently, these multilayers may be useful in media for perpendicular magnetic/magneto-optical two-way magnetic recording systems.

Investigation of magnetization reversal mechanism in nanometer-thick Tb-Fe-Co films with Al overlayer

Magnetic anisotropy energy and magnetization reversal mechanism were investigated in the glass/Tb-Fe-Co(MO)/Al films with the MO layer thickness t/sub MO/ 3 to 10 nm. As t/sub MO/ decreases, an easy magnetization direction changed from perpendicular to parallel to a film plane at t/sub MO/ of about 4 nm. Measurements of rotational hysteresis loss suggested that the magnetization reversal in the films seems to be an incoherent curling mode.

Magnetic and optical characteristics of bilayered films composed of Tb‐Fe‐Co layer with overlayers of Co‐Cr, Ni‐Fe, Ta, and C

Amorphous Tb‐Fe‐Co single layers and Tb‐Fe‐Co/M (M: Ta, C, Co82Cr18, Ni81Fe19) bilayers have been prepared by using a facing targets sputtering apparatus. The Tb‐Fe‐Co films deposited by Kr sputtering exhibited internal stress as low as 1×109 dyn/cm2 even at a pressure as low as 0.2 mTorr. The Tb‐Fe‐Co/Ta bilayers showed a Kerr rotation angle as large as 0.85° at the thickness of Tb‐Fe‐Co layer of about 30 nm. The direction of magnetic moments in Tb‐Fe‐Co layers were arranged antiparallel by a soft magnetic Ni81Fe19 overlayer.

Magnetic and magneto-optical properties of Tb-Fe-Co/Ta multilayers

Tb-Fe-Co/Ta multilayers were deposited on plasma-free glass slide substrates by using a facing targets sputtering apparatus. The specimen films with very thin thickness of Ta layers less than 1 nm revealed flat and sharp interfaces. The enhancement of Kerr rotation angle was increased with decreasing thickness of paramagnetic Ta layer. The magnetic interaction between Tb-Fe-Co layers were observed even in the multilayers with the thickness of Ta layers approaching 20 nm. >

Distribution of magnetic field in facing targets sputtering apparatus with Tb-Fe-Co and Al targets

The distribution of the magnetic field in the facing targets sputtering apparatus have been measured by using a gaussmeter and calculated by computer aided finite element method. The measured radial field distribution at the central plane between two facing targets agreed well with calculated one. It was shown that the size of permanent magnets for confining plasma may influence the strength of magnetic field but may not do the distribution of magnetic flux.

Optimization of magnetic field in facing targets sputtering apparatus for preparing Co-Cr tape media

Distribution of magnetic field in facing targets sputtering (FTS) apparatus have been measured by using a gaussmeter. Perpendicular line of force between target planes and extremely high magnetic field above target edge confined plasma almost perfectly and substrates could be placed in plasma-free region even for ferromagnetic targets. Parameters important for controlling distribution and strength of magnetic field in FTS system seemed to be distance between targets, target magnetism, performance of magnet and distance between target and magnet, in order of influence degree.