Depth-Adjustable Magnetostructural Phase Transition in Fe₆₀V₄₀ Thin Films

Abstract

Phase transitions occurring within spatially confined regions can be useful for generating nanoscale material property modulations. Here we describe a magneto-structural phase transition in a binary alloy, where a structural transition from short-range order (SRO) to body centered cubic (bcc) results in the formation of depth-adjustable ferromagnetic layers, which reveal application-relevant magnetic properties of high saturation magnetization (M s) and low Gilbert damping (α). Here we use Fe60V40 binary alloy films which transform from initially M s = 17 kA/m (SRO structure) to 747 kA/m (bcc structure) driven by atomic displacements caused by penetrating ions. Simulations show that an estimated ∼1 displacement per atom triggers a structural transition, forming homogeneous ferromagnetic layers. The thickness of a ferromagnetic layer increases as a step-like function of the ion fluence. Microwave excitations of the ferromagnetic/non-ferromagnetic layered system reveals an α = 0.0027 ± 0.0001. The combination of nanoscale spatial confinement, low α, and high M s provides a pathway for the rapid patterning of magnetic and microwave device elements.

Resonance behavior of embedded and freestanding microscale ferromagnets

“…Therefore, the selective material removal can provide another pathway for the local modification of resonant properties, in addition to the local disordering of the B2 Fe 60 Al 40 template material itself. Indeed, embedded ferromagnetic regions have recently been obtained on other template materials [43][44][45][46] . An amplification of stray field effects can be expected in dipolarly coupled objects, since the coupling is reliant entirely on the stray field alone.…”

Transport properties of Fe60Al40 during the B2 to A2 structural phase transition

“…Applications such as magnetic data storage as well as magnetic sensors and spin-transport devices require a precise control of intrinsic magnetic properties at the nano-and meso-scales [1]. An important property is the saturation magnetization, which can be tuned using ion-irradiation induced lattice disordering [2][3][4][5]. Typically, modifications using ion irradiation tends to be a destructive process whereby the penetrating ions suppress lattice ordering, leading to a reduced exchange coupling [3,[6][7][8][9].…”

Laser‐Induced Positional and Chemical Lattice Reordering Generating Ferromagnetism

“…Subtle changes in both positional and chemical order have been demonstrated to yield significant modifications in the material's optical properties, for example, reflectance, as well as in the magnetic behavior, such as the exchange coupling, and can result in the onset of ferromagnetism. [8][9][10] These alterations to the functional material properties described above can be induced by single-pulsed femtosecond (fs) laser irradiation [9] and can be tracked in the ultrafast time regime by applying pump-probe metrology. [11][12][13][14][15] This approach provides insights into the pathways leading to lattice reordering.…”

“…[7,8,16,17] In contrast, the second alloy, Fe 60 V 40 , exhibits positional and chemical disorder in its initial state (Figure 1, right). [10,[18][19][20][21] By modifying the chemical order in both alloys through energy deposition via penetrating ions [8,16,[22][23][24] or laser irradiation, [7,9,25] a formation into a positionally ordered but chemically disordered state, referred to as A2 phase, can be induced (Figure 1, irradiated areas). [8,9,16] This phase transition is accompanied by an increased nearest-neighbor coordination and the onset of localized ferromagnetism in the positionally ordered and chemically disordered regions as indicated by the white arrows in Figure 1.…”

“…Subtle changes in both positional and chemical order have been demonstrated to yield significant modifications in the material's optical properties, for example, reflectance, as well as in the magnetic behavior, such as the exchange coupling, and can result in the onset of ferromagnetism. [ 8–10 ]…”