Ion beam induced modification of exchange interaction and spin–orbit coupling in the Co₂FeSi Heusler compound

Abstract

Abstract.A Co 2 FeSi (CFS) film with L2 1 structure was irradiated with different fluences of 30 keV Ga + ions. Structural modifications were subsequently studied using the longitudinal (LMOKE) and quadratic (QMOKE) magneto-optical Kerr effect. Both the coercivity and the LMOKE amplitude were found to show a similar behavior upon irradiation: they are nearly constant up to ion fluences of ≈ 6 × 10 15 ion/cm 2 , while they decrease with further increasing fluences and finally vanish at a fluence of ≈ 9×1016 ion/cm 2 , when the sample becomes paramagnetic. However, contrary to this behavior, the QMOKE signal nearly vanishes even for the smallest applied fluence of 3 × 10 14 ion/cm 2 . We attribute this reduction of the QMOKE signal to an irradiationinduced degeneration of second or higher order spin-orbit coupling, which already happens at small fluences of 30 keV Ga + ions. On the other hand, the reduction of coercivity and LMOKE signal with high ion fluences is probably caused by a reduction of the exchange interaction within the film material.

Thickness dependence of linear and quadratic magneto-optical Kerr effects in ultrathin Fe(001) films

“…33͒ recently found in Co 2 FeSi alloys in Ref. 34. These comparable orders of magnitudes of the QMOKEs of Fe and Co 2 FeSi imply that the maximum QMOKE value of Fe in the visible wavelength region might be even larger than that of Co 2 FeSi as both materials are expected to have distinct frequency dependences resulting from their electronic band structures.…”

Magneto-optical investigation of epitaxial nonstoichiometric Co2MnGe thin films

“…This suggests that the electronic properties of this sample are well described by a cubic environment, as expected for a Heusler compound. [19][20][21][22][23] The solid lines in Fig. 5 are fits to the various components of Eq.…”

“…16,18 In this context, the knowledge of the exchange stiffness, which will largely determine the energy required to create a spin wave, is a crucial parameter that must be understood to gain insight into the construction of superior devices. As a part of our ongoing investigation of the magnetooptical properties of Co 2 -based Heusler compounds by means of magneto-optical Kerr effect ͑MOKE͒ magnetometry [19][20][21][22][23] and Brillouin light scattering ͑BLS͒ spectroscopy, 19,[24][25][26] we here report on the investigation of the Mn-and Ge-deficient, nonstoichiometric epitaxial Co 2 Mn 0.77 Ge 0.42 films described above. The compound of interest here, Co 2 MnGe, was recently investigated by BLS spectroscopy.…”

Quadratic magneto-optic Kerr effect spectroscopy of Fe epitaxial films on MgO(001) substrates

“…Nevertheless, to employ QMOKE measurements on a regular basis, the underlying origin of QMOKE must be well understood. Although QMOKE effects have been already studied, especially in the case of Heusler compounds [16][17][18][19][20][21][22][23], all the studies employ single wavelengths only. The MOKE spectroscopy together with ab-initio calculations is an appropriate combination to gain a good understanding of the microscopic origin of MO effects.…”