AVS 62nd International Symposium & Exhibition
    Thin Film Thursday Sessions
       Session TF+AS+NS+SA-ThA

Paper TF+AS+NS+SA-ThA11
Tuning Static and Dynamic Magnetic Properties of FeGa/NiFe Multilayer Composites

Thursday, October 22, 2015, 5:40 pm, Room 111

Session: Thin Film: Growth and Characterization, Optical and Synchrotron Characterization II
Presenter: Colin Rementer, University of California at Los Angeles
Authors: C. Rementer, University of California at Los Angeles
Q. Xu, University of California at Los Angeles
K. Fitzell, University of California at Los Angeles
Z. Yao, University of California at Los Angeles
P. Nordeen, University of California at Los Angeles
G. Carman, University of California at Los Angeles
Y. Wang, University of California at Los Angeles
J.P. Chang, University of California at Los Angeles
Correspondent: Click to Email
Traditionally, the use of magnetic materials in high frequency applications has been limited to oxides. This is because the materials’ high resistivity, which reduces the formation of eddy currents by the incident electromagnetic waves. However, these oxides have limited applications in multiferroics, which are materials that possess more than one ferroic ordering in a single phase or strain-coupled composite systems, due to their low magnetomechanical coupling. Metallic materials are more desirable to this end, but their magnetic hardness and conductive losses have limited their use.

Rare-earth-free iron-gallium (FeGa) is one of the most promising magnetostrictive materials for use in composite multiferroics, due to its high piezomagnetic coefficient (3 ppm/Oe) and high stiffness (70 GPa). It has been integrated into several multiferroic systems, but generally in the MHz range or below1. This is due to the fact that the material has a large ferromagnetic resonance (FMR) linewidth (>300 Oe) at X band (9.6 GHz), which will result in incident energy being converted to heat. Metalloid dopants have been used to soften magnetic materials and to tune frequency dependent properties, such as permeability and piezomagnetic behavior, but at the cost of saturation magnetization as well as magnetostriction2. In this work, multilayer laminates containing alternating hard and soft ferromagnetic layers were fabricated to reduce loss at high frequencies.

FeGa (hard) and NiFe (soft) were sputtered via alloy targets into multilayers on Si [100] and piezoelectric substrates with total thicknesses ranging from 40-500 nm. The compositions of the films were verified via X-ray photoelectron spectroscopy (XPS) and were found to be FeyGa1-y (78≤y≤85 at%) and NixFe1-x (79≤x≤83 at%). Static magnetic properties were evaluated via superconducting quantum interference device (SQUID) magnetometry, and it was found that the incorporation of NiFe layers was found to reduce the coercivity by up to 80%, while only reducing the saturation magnetization by 20%. FMR measurements revealed a narrowing of the linewidth by up to 90% at X band. Permeability extracted from the reflection coefficient (S11) obtained via stripline measurement was found to be affected by layer thickness and number of layers. FeGa showed strong magnetoelastic behavior and the multilayers are expected to exhibit an enhanced piezomagnetic effect due their reduced coercivity.

References:

1.M. Hamashima, C. Saito, M. Nakamura and H. Muro, Electr Commun Jpn 95 (5), 1-7 (2012).

2.J. Lou, R. E. Insignares, Z. Cai, K. S. Ziemer, M. Liu and N. X. Sun, Appl Phys Lett 91 (18) (2007).