Magnetic states controlled by energetic ion irradiation in FeRh thin films

Abstract

Changes in magnetic properties and lattice structure of FeRh films by 180 keV–10 MeV ion (H, He, and I) irradiation are studied. In spite of the irradiation with different ion species and wide range of energies, the changes in magnetization are dominated by solely a single parameter; the density of energy which is deposited through elastic collision between the ions and the samples. For the low deposition energy density, the magnetization increases with increasing the deposition energy density, while the lattice structure remains unchanged. When the deposition energy density becomes larger, however, the magnetization decreases after reaching the maximum value. The decrease in the magnetization accompanies the crystal structure change from B2 to A1. The present results imply that the magnetic state of FeRh films can be designedly controlled by the energetic ion irradiations.

Tuning the antiferromagnetic to ferromagnetic phase transition in FeRh thin films by means of low-energy/low fluence ion irradiation

“…This indicates an increasing ferromagnetic background induced by the ongoing chemical disordering. This explains the drastic increase of the saturation magnetisation at 20 K as observed by other groups [15,16]. For our films, the increase of the ferromagnetic signal, i.e.…”

“…In accordance with [15,16], the intensity of the (0 0 1) B2 superstructure peak is influenced more strongly than the peaks that are not sensitive to the chemical order. This change of the chemical order can be qualitatively estimated from the XRD data using the ratio between the integrated intensities of the superstructure peaks and the fundamental peaks.…”

“…In Refs. [15,16], no change of lattice constant due to ion irradiation was reported. The same fact is valid for our samples.…”

“…Recently it was found that chemical disorder introduced into FeRh thin films by means of ion irradiation with either H (1 MeV) or I (10 MeV) ions leads to an increasing ferromagnetic signal at low temperatures. The saturation magnetisation measured at 20 K increases monotonically with fluence before decreasing due to the formation of the A1 phase [15]. It was found that already a small decrease of the ordering parameter of about 9% achieved, e.g.…”

Ferromagnetism at the interfaces of antiferromagnetic FeRh epilayers

“…6,7 A significant magnetoresistance of 90% was found for bulk FeRh at room temperature and up to 1700% at 4.2 K for polycrystalline FeRh. 8 The transition may be affected and hence controlled by many factors, including the applied magnetic field, 9 ion-irradiation, 10 stress state, 11 and the sample microstructural scale. 12 In nanoscale film form it is of great interest for potential applications in heat-assisted magnetic recording, 13 magnetic refrigeration, 13 and ultrafast ͑ps͒ switching.…”