Dependence of the Magnetization Process on the Thickness of Fe70Pd30 Nanostructured Thin Film.

Mohamed Salaheldeen,Pablo Álvarez-Alonso,Seraj Omar Alzahrani,Ahmed Mohamed Abu-Dief,Lucía Martínez-Goyeneche,Fatmah Alkhatib,Jesús Ángel Blanco

doi:10.3390/ma13245788

Mohamed Salaheldeen, Pablo Álvarez-Alonso + Show 5 more

Open Access

https://doi.org/10.3390/ma13245788

Copy DOI

Abstract

Fe–Pd magnetic shape-memory alloys are of major importance for microsystem applications due to their magnetically driven large reversible strains under moderate stresses. In this context, we focus on the synthesis of nanostructured Fe70Pd30 shape-memory alloy antidot array thin films with different layer thicknesses in the range from 20 nm to 80 nm, deposited onto nanostructured alumina membranes. A significant change in the magnetization process of nanostructured samples was detected by varying the layer thickness. The in-plane coercivity for the antidot array samples increased with decreasing layer thickness, whereas for non-patterned films the coercive field decreased. Anomalous coercivity dependence with temperature was detected for thinner antidot array samples, observing a critical temperature at which the in-plane coercivity behavior changed. A significant reduction in the Curie temperature for antidot samples with thinner layer thicknesses was observed. We attribute these effects to complex magnetization reversal processes and the three-dimensional magnetization profile induced by the nanoholes. These findings could be of major interest in the development of novel magnetic sensors and thermo-magnetic recording patterned media based on template-assisted deposition techniques.

Highlights

Fe–Pd alloy thin films have attracted interest due to their various functional properties: strong effective uniaxial magnetic anisotropy, large saturation magnetization, high magneto-optic Kerr rotation behavior [1], magnetic behavior [2], biocompatibility [3,4], mechanical properties [5] and wettability properties [6].In particular, Fe–Pd alloys containing about 30 at.% Pd are promising magnetic shape-memory alloys, since they show a ferromagnetic character at room temperature [7,8,9]
The shape-memory effect is based on the reorientation of the twin variants of the martensite phase associated with Fe–Pd alloys [11] and can be controlled by temperature and stress
Ordered antidot arrays of Fe70 Pd30 alloy thin films formed by highly pure metal pieces of Fe (Goodfellow Limited, Cambridge, UK, 99.9% purity) and Pd (Ventron GMBH, Dortmund, Germany, 99.99% purity) were deposited on the Nanoporous anodic alumina templates (NPAATs) substrates by an ultra-high vacuum thermal evaporator (Edwards E306A, Manor Royal, Crawley, West Sussex, UK) at pressures below 10−7 mbar, as described in [25,26,27], with a film thickness in the range of 20 nm ≤ t ≤ 80 nm

Summary

Introduction

Fe–Pd alloys containing about 30 at.% Pd are promising magnetic shape-memory alloys, since they show a ferromagnetic character at room temperature [7,8,9]. These shape-memory alloys are smart materials that, due to their potential applications, have attracted a great deal of attention from materials researchers—especially in wireless actuated micro/nanoelectromechanical systems, magneto-mechanical actuators and sensors [9,10]. The shape-memory effect is based on the reorientation of the twin variants of the martensite phase associated with Fe–Pd alloys [11] and can be controlled by temperature and stress. The combination of magnetic and martensitic order makes this metallic multiferroic material a promising candidate for applications in micro- and nanodevices [10]

Objectives

Methods

Results

Conclusion