| High magnetic performances, such as high Curie temperature, high magnetocrystalline anisotropy(MCA), and high perpendicular magnetic anisotropy(PMA) of the magnetic thin films, are important and prerequisite magnetic properties for the advanced magnetic materials including permanent magnet material used under high temperature environment, and ultra-high density perpendicular magnetic recording material. The rare earth transition metal(RE-TM) alloys and Fe Co based [Fe Co/RE]N multilayers have attracted increasing research interest because they have excellent magnetic properties. It has become the focus due to the widely application in perpendicular magnetic recording materials and computer hard disk.In this paper, the magnetic properties of the sputtered [Tb/Fe Co]3/Tb/Fe Mn multilayers with PMA and perpendicular exchange bias(P-EB), and other magnetic properties of magnetron sputtered Nd Co and Nd Co Fe B alloy films are systematically studied. The main results are as follows:1. PMA and P-EB effects of [Tb/Fe Co]3/Tb/Fe Mn multilayers prepared by magnetron sputteringFirstly, the influences of Fe Mn covering layer and Fe Mn buffer layer on the magnetic properties of the [Tb/Fe Co]3 multilayer with PMA have been studied. It has been found that Fe Mn covering layer leads to a change of two-step M-H loop of the[Tb/Fe Co]3 multilayer films into a one-step loop measured at the applied field perpendicular to the film plane, and the normal coercivity is decreased. Also, the unusual magnetization reversal process(at low field part) is suppressed. It is suggested that Fe Mn covering layer enhances the interlayer exchange coupling of[Tb/Fe Co]3/Fe Mn multilayer, and improves the degree of the orientation of the magnetic moment in the direction perpendicular to the film surface.Secondly, the influences of the ultra thin Tb spacer between Fe Mn sublayer and[Tb/Fe Co]3 multilayer on the PMA and P-EB effects of the [Tb/Fe Co]3/Tb/Fe Mn multilayer have been studied. It has been shown that position of the ultra thin Tb spacer on the top of the Fe Mn buffer layer is more effective to enhance the perpendicularcoercivety and PMA than the position of Tb spacer inserted under Fe Mn coverlayer.After the samples have been annealed under the magnetic field applied perpendicular to the film surface, the value of the coercivety Hc increases first with the annealing temperature and reaches the maximum at Ta = 170 o C, then decreases at Ta = 200 o C.In the AF/FM/AF type of the Si(111)/Cu(33)/Fe Mn(25)/Tb(0.4)/[Fe Co(1.5)/Tb(5)]3/Tb(0.4)/Fe Mn(25)/Cu(33) multilayer film system, it has been found that the perpendicular exchange bias field about HIIEB = 183 Oe induced mainly by the intermediate Fe Co sublayer in the [Fe Co(1.5)/Tb(5)]3 multilayer is larger than the P-EB of HIEB = 86 Oe induced mainly by the Fe Co layers adjacent to the Fe Mn layer. The larger P-EB effect of the intermediate Fe Co layer may be attributed to the compensation interface exchange coupling between ferromagnetic and ferrimagnetic FM-Fi interface in [Fe Co(1.5)/Tb(5)]3 multilayer. The compensational coupling in the FM-Fi interface may be stronger than the uncompensation coupling in the AF/FM interfaces.2. PMA and related magnetic properties of magnetron sputtered Nd Co and Nd Co Fe B alloy filmsA series of Si(111)/Cr/Nd Cox(500nm) /Cr, x=2.5, 2.8, 4.4, 7.2 alloy films were prepared by magnetron sputtering, and then the effect of the alloy composition on the PMA was studied. The results show that the perpendicular anisotropy(K?) of the deposited amorphous Nd Cox films with the thickness about t = 500 nm increases with the Co/Nd atomic ratio of x and saturates near x = 4. The magnetic force microscopy(MFM) measurements show that the MFM of the deposited alloy films with x=4.4exhibits a periodic stripe domain structure, and the MFM of the films with x =2.8showed an irregular pattern of sand dunes. After rapid thermal annealing at 600 and 700 DEG, the precipitation of the nanocrystallines of Nd2Co17, Co and Co Cr interfacial alloy phase have been observed by XRD measurements on the Nd Cox alloy films studied here. Besides, some nano crystalline grains of Nd Co3 and Nd Co5 compounds were also observed in the annealed films with x < 4. The precipitation of the hard magnetic alloy phases has also been confirmed by VSM measurements, which show that the in-plane coercivity of the annealed films with x = 4.2 and 7.2 at Ta = 700 Degree is low(about Hc = 105 and 88 Oe, respectively), while the coercivity of the films with x = 2.5 and 2.8annealed at the same temperature by RTA show much high values of the Hc = 1357 and1120 Oe, respectively, due to the precipitation of Nd Co3 and Nd Co5 hard magnetic alloys.It has been observed that the PMA of the deposited Si(111)/Cr/Nd Co Fe B(t)/Cr filmis sensitive to the composition and the content of the B and Fe elements added into Nd Co alloy. Among 4 kinds of samples(noted as I to IV) with different alloy components studied here, the II-Nd(Fe8.95Co91.05)2.19B6.57 film shows the largest perpendicular anisotropy of K?=2.6×105 J/m3. With the more addition of Fe element, the PMA of the Nd Co Fe B alloy film shows downward trend. After RTA annealing at 700 degree, some crystalline grains, such as Nd Co5 Nd Co3 Co3 b and Nd2Co14 B Nd Co4 B hard magnetic alloys have been precipitated in the sample of III-Si/Cr(33 nm)/Nd(Fe15.68Co84.32)2.36B6.19(480 nm)/Cr(33 nm) film. The in-plane M-H Loop measured at RT shows large coercivety about HC =7690 Oe. |
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