Direct observation of magnetic gradient in Co/Pd pressure-graded media

Abstract

Magnetometry and neutron scattering have been used to study the magnetic properties of pressure graded Co/Pd multilayers. The grading of the multilayer structure was done by varying the deposition pressure during sputtering of the samples. Magnetic depth profiling by polarized neutron reflectometry directly shows that for pressure-graded samples, the magnetization changes significantly from one pressure region to the next, while control samples sputtered at uniform pressure exhibit essentially uniform magnetic depth profiles. Complementary magnetometry results suggest that the observed graded magnetic profiles are due in part to a decrease in saturation magnetization for regions deposited at progressively higher pressure. Increased deposition pressure is shown to increase coercivity, and for graded samples, the absence of discrete steps in the hysteresis loops implies exchange coupling among regions deposited at different pressures.

First-order reversal curve analysis of graded anisotropy FePtCu films

“…There have been few reports, mostly based on rather thick multilayered structures, on the successful creation of graded materials. [10][11][12][13][14] However, the realization of a continuous anisotropy gradient was recently achieved in properly annealed compositionally graded thin FePtCu films. 15 In conjunction with the fabrication, the subsequent analysis of graded materials is not trivial and often requires complicated measurement apparatuses.…”

“…For example, the inherent depth sensitivity of polarized neutron reflectivity measurements has recently been used to directly probe the anisotropy gradient of multilayered Co/Pd samples. 12,13 In this letter, we report on a relatively simple measurement and analysis technique that combines first-order reversal curve ͑FORC͒ [16][17][18][19][20][21][22] measurements with the inherent surface sensitivity of the magneto-optical Kerr effect ͑MOKE͒ to analyze FePtCu films with a continuously graded anisotropy. In addition to providing a useful qualitative fingerprint of the magnetization reversal mechanisms, the FORC techniques are able to extract a wealth of quantitative information not readily accessible from standard major loop or remanence curve analysis.…”

Continuously graded anisotropy in single (Fe53Pt47)100−xCux films

“…Fabrication of graded media, in particular the realization of a continuous gradient, is challenging and has, until now, been based on multilayered structures. [14][15][16][17][18] In this letter, we report on a simple approach to fabricate continuously graded-K u single films based on the strong dependence of the A1 ͑low K u ͒ → L1 0 ͑high K u ͒ ordering temperature on the Cu content in ͑Fe 53 Pt 47 ͒ 100−x Cu x ͑x =0-30͒ films. 19 First, a compositional gradient is achieved by varying the Cu concentration from Cu-rich ͑Fe 53 Pt 47 ͒ 70 Cu 30 at the bottom to Cu-free Fe 53 Pt 47 at the top during film deposition, as schematically represented in Fig.…”

Probing vertically graded anisotropy in FePtCu films

“…Fabrication schemes to realize graded films remain few and have mostly relied on multilayered approaches. [14][15][16][17][18][19] However, a continuous anisotropy gradient has been recently realized in properly annealed, compositionally graded FePtCu films. 20,21 In addition, similar FePtCu films have been shown to have a tilted anisotropy 22,23 that, when combined with the advantages of graded anisotropy, may result in versatile material suitable for both magnetic recording and spin transfer torque applications.…”