Engineering new limits to magnetostriction through metastability in iron-gallium alloys

Abstract

Magnetostrictive materials transduce magnetic and mechanical energies and when combined with piezoelectric elements, evoke magnetoelectric transduction for high-sensitivity magnetic field sensors and energy-efficient beyond-CMOS technologies. The dearth of ductile, rare-earth-free materials with high magnetostrictive coefficients motivates the discovery of superior materials. Fe1−xGax alloys are amongst the highest performing rare-earth-free magnetostrictive materials; however, magnetostriction becomes sharply suppressed beyond x = 19% due to the formation of a parasitic ordered intermetallic phase. Here, we harness epitaxy to extend the stability of the BCC Fe1−xGax alloy to gallium compositions as high as x = 30% and in so doing dramatically boost the magnetostriction by as much as 10x relative to the bulk and 2x larger than canonical rare-earth based magnetostrictors. A Fe1−xGax − [Pb(Mg1/3Nb2/3)O3]0.7−[PbTiO3]0.3 (PMN-PT) composite magnetoelectric shows robust 90° electrical switching of magnetic anisotropy and a converse magnetoelectric coefficient of 2.0 × 10−5 s m−1. When optimally scaled, this high coefficient implies stable switching at ~80 aJ per bit.

Giant converse magnetoelectric effect in a multiferroic heterostructure with polycrystalline Co2FeSi

“…In Table 1, we summarize the reported values of the giant α E for various multiferroic heterostructures and compared them to those of this study. Apart from the Fe 50 Rh 50 / BaTiO 3 (001) system 22 , a giant CME effect was observed in various FM/PMN-PT systems 28,34,35 . As previously described, because ferroelectric PMN-PT has a piezoelectric constant 43 that is relatively large compared to that of BaTiO 3 , a large piezostrain can be induced from PMN-PT to FM layers via multiferroic heterointerfaces [26][27][28][29]34,35 .F o r magnetostrictive materials such as Fe 1-x Ga x ,o n eh a st o achieve a metastable bcc (A2) phase with x ~30%asasingle crystalline film on PMN-PT to obtain a giant α E of more than 1.0 × 10 −5 s/m 35 .…”

“…5a. In the relevant fields, an α E of more than 1.0 × 10 −5 s/m has thus far been reported in multiferroic heterostructures consisting of PMN-PT substrates and single-crystalline magnetostrictive materials such as FeRh 22 and FeGa alloys 34,35 . On the other hand, we observe the giant α E of more than 1.0 × 10 -5 s/m even in the polycrystalline Co 2 FeSi/PMN-PT(011) heterostructure, where Co 2 FeSi is one of the most representative spintronic Co-based Heusler alloys 38,39 .…”

“…With respect to the giant ME coupling coefficients of more than 1.0 × 10 −5 s/m, single-crystalline Fe 1-x Ga x alloys grown on PMN-PT are promising materials 34,35 ,a s Fe 1-x Ga x alloys are good magnetostrictive materials for strain sensors, actuators, and energy harvesters 36,37 .H o wever, spin polarization at the Fermi level of Fe 1-x Ga x alloys is less than that of spintronic materials 36 .T h u s ,h i g hperformance spintronic materials, such as FM half-metals grown on PMN-PT, should be explored to realize magnetization switching with ultralow power consumption [23][24][25] . Here, we have chosen Co-based Heusler alloys, since they are expected to be half-metallic materials with high Curie temperatures [38][39][40] .I nt h i sw o r k ,w ef o c u sp a rticularly on Co 2 FeSi as an FM material because the L2 1 -ordered Co 2 FeSi has already shown a half-metallic nature [40][41][42] .…”

Magnetic control over the fundamental structure of atomic wires

“…Magneto-structural effects, such as magnetostriction 9 – 11 and piezomagnetism 12 – 14 are manifested as changes in the dimensions of magnetic materials in response to an applied magnetic field. These effects have diverse scientific and technological implications, either as undesirable effects in accurate measurements and device operation, or as means to achieve mechanical action via magnetic stimuli 15 – 18 . Since they are not limited to a specific length-scale, such effects can be observed, in principle, in nanometer-sized materials.…”

Strain driven phase transition and mechanism for Fe/Ir(111) films

“…Iron and iron-based alloys are the most important materials used in magnetic devices, such as magnetic tunnel junction 26 – 28 , magnetic random access memory 29 , 30 and magnetic sensors 31 – 33 . Because of their different lattice structures, Fe/Ir interfaces function as a platform for controlling pseudomorphic growth, nanostructure evolution, and the formation of strained clusters.…”