Vertically graded anisotropy in Co/Pd multilayers

Abstract

Depth-grading of magnetic anisotropy in perpendicular magnetic media has been predicted to reduce the field required to write data without sacrificing thermal stability. To study this prediction, we have produced Co/Pd multilayers with depth-dependent Co layer thickness.Polarized neutron reflectometry shows that the thickness grading results in a corresponding magnetic anisotropy gradient. Magnetometry reveals that the anisotropy gradient promotes domain nucleation upon magnetization reversal -a clear experimental demonstration of the effectiveness of graded anisotropy for reducing write-field.

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 16-22 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.…”

Accessing different spin-disordered states using first-order reversal curves

“…It is often useful to evaluate the irreversible switching using the FORC-switching field distribution (FORC-SFD). This is accomplished by projecting the FORC distribution onto the H R axis, equivalent to an integration over the applied field H [25,48],…”