Studies On Microstructures And Magnetic Properties Of (Ag)/Co/Ag Thin Films

Four series Ag/Co/Ag quasi-sandwich nanocomposite magnetic films are fabricated by magnetron sputtering onto glass substrates at room temperature. The magnetic properties and microstructure of these films have been investigated in detail by VSM, XRD and SPM.It has been found that the microstructures and magnetic properties of Ag/Co/Ag films depend strongly on the thickness of Ag layer and Co magnetic layer at room temperature.For the series of Ag(t)/Co(15nm)/Ag(t)(t=1,2,3,4,5nm)films, when the Ag layer thickness is 4nm, VSM measurements indicate that the out-of-plane coercivity reaches the maximum and SPM image shows that the average grain size is about 30 nm .XRD profiles show that the Ag layers are formed as the face-center-cubic (fcc) structure in as deposited films and that the Co layer formed as hexagonal-close-packed (hcp) structure.The series of Ag(t=4nm)/Co(t nm)/Ag(4nm) (t=5,10,15,20nm)films were prepared by dc magnetron sputtering onto glass substrates at room temperature. VSM measurements indicate that when the Co layer thickness is 15 nm, the out-of-plane coercivity reaches the maximum about 449Oe, SPM image shows the average grain size is 30nm.It has been found that the microstructure and magnetic properties of Ag (4nm)/Co (15nm)/Ag (4nm) films depend strongly on the post annealing temperature. The hexagonal-close-packed (hcp) structure is dominant in all annealed films. Annealed at 400?C, the domain size is the smallest. The coercivity reaches the maximum about 1.28kOe. TheδM curve shows the negative value for the annealed film, which indicates that intergrain-interaction change from exchange-interaction to dipolar-interaction.Co (15nm)/Ag (4nm) films have been fabricated using a dc facing magnetron sputtering method. The films are annealed at different temperatures. It has been found that Co layer is formed as hexagonal-close-packed (hcp) structure in all annealed films. For the annealed films, theδM curves indicate intergrain-interaction is dipolar-interaction. Annealed at 400?C, the coercivity reaches the maximum about 570Oe. It is suggested that Ag over layer strongly affect the coercivity. We think that the Ag atoms in Ag/Co/Ag film can more effetely defuse into the barrages of the Co grain boundary.