Unusual magnetization characteristics of Fe-Ni films with graded composition

Abstract

Stress dependence and effect of plastic deformation on magnetic hysteresis and anhysteretic magnetization of FeNi32% filmsThin films of Fe-Ni with graded composition have been deposited on a Si (001) substrate at room temperature by co-sputtering of Fe and Ni with variable rates of the constituting elements. The composition of the films was changing linearly across the thickness from Fe 80 Ni 20 to Fe 6 Ni 94 . Five samples were studied with the thickness of 30, 50, 100, 150, and 200 nm. The hysteresis loops measured with the field applied in the film plane had square shape and the coercivity was varying from 11 to 22 Oe. However, the loops for the field perpendicular to the film plane displayed unusual shapes consisting of a double-step hysteresis loop at low fields and unhysteretic part at higher fields. The size of the steps varied with the thickness of the film. The most likely source of the double step hysteretic curves was identified as magnetostrictive stresses at the film/substrate interface. This was evidenced by the disappearance of the second hysteresis step after annealing at 200 C for 1 h and significant changes of the hysteresis loops when the same structure was deposited starting from Fe-rich or Ni-rich compositions at the substrate.

Structural properties of Fe-Ni/Cu/Fe-Ni trilayers on Si (100)

“…The crystal structure and magnetism of Fe-Ni thin films strongly depend on Ni content 20,21 . The physical properties of Fe-Ni films are also known to vary with the surface morphology and texture of the films 22,23 . The onset of interdiffusion in thick FeNi and Cu multilayers starts at around 200 0 C 24 .…”

Formation of bcc and fcc during the coalescence of free and supported Fe and Ni clusters

“…1 Fe-Ni films having high anisotropic magnetoresistance (AMR) properties, high saturation magnetization and low coercivity are one of the most important soft magnetic materials. 6,7 Structurally, Fe-Ni films exist as bcc, fcc and L1 0 depending on Ni content and result in differences to the films' magnetic properties. 6,7 Structurally, Fe-Ni films exist as bcc, fcc and L1 0 depending on Ni content and result in differences to the films' magnetic properties.…”

“…[2][3][4][5] Magnetic properties of Fe-Ni films vary as a function of Ni content and can be further modified by changes in the surface morphology and the microstructure of the films. 6,7 Structurally, Fe-Ni films exist as bcc, fcc and L1 0 depending on Ni content and result in differences in the magnetic properties of films. 8,9 Fe-Ni (fcc) films exhibit the highest magnetization values (1270 emu cm À3 ).…”