Ultrafast modulation of exchange-coupling induced anisotropy in Fe/CoO by laser induced charge transfer

Abstract

Optical control of magnetic anisotropy in ferromagnetic (FM) metals via non-thermal effects offers an intriguing route for the ultrafast magnetization control. Here, we report on strong modification of exchange-coupling induced uniaxial magnetic anisotropy (UMA) in Fe/CoO below the Néel temperature of CoO owing to the charge transfer excited by ultrafast laser pulses. This UMA modification by nonthermal effects is manifested as much smaller frequencies of the Fe spin precession in the initial 100-ps time range under the 400-nm pump with charge transfer excitation, compared to the 800-nm pump with pure thermal effects. From the time-dependent frequency shift under a moderate pump fluence of 0.5 mJ/cm2, we determined the magnitude of the UMA attenuation with a highest value of more than 1000 Oe in a duration of 100 ps. The strong UMA attenuation is attributed to the large suppression of the interface exchange coupling as a result of the diminishment of antiferromagnetic (AFM) spin order in CoO. Our results give insights into the ultrafast spin modulation in AFM CoO dominated by the electronic process, which can be utilized for efficient driving of the coherent spin motion in the proximate FM metal exchange coupled to CoO.

Resonant Pumping of d−d Crystal Field Electronic Transitions as a Mechanism of Ultrafast Optical Control of the Exchange Interactions in Iron Oxides

“…This scenario is illustrated in Fig. 1c and has been discussed earlier for manganites [33] and ferromagnetic/antiferromagnetic heterostructures [34,35].…”

Antiferromagnetic spin dynamics in exchanged-coupled Fe/GdFeO3 heterostructure*

“…The impact of the high fluence on Fe film is comparatively large such as heat transport effect or the destruction of the magnetic anisotropy [32] resulting in the magnetic disorder or charge redistribution. [33][34][35] Therefore, weakening of the amplitude may come from the moment destruction or the charge redistribution by the intensive laser, leading to the saltation of the exchange coupling. However, the microscopic mechanism for optical modification of interfacial exchange coupling and the impact on magnetic order needs more experimental and theoretical studies.…”

Effect of metal insertion on the magnetic properties and anomalous Hall effect in MgO/CoFeB/Ta/MgO films

“…For example, by applying an external electric field that perpendicular to the film surface, the electron density at the interface of ferromagnetic layer changes, leading to transformation of the magnetic anisotropy and realizing electric field manipulation of magnetic tunnel junction reversible switch [27]. The pump pulse generated by the laser pulse irradiating the thin film will cause the charge transfer in the material and affect the exchange coupling at the ferromagnetic/oxide interface to further tune the magnetic anisotropy [28]. The first-principles calculation demonstrates that PMA is derived from the hybridization of the ferromagnetic metal 3d and O 2p orbitals at the ferromagnetic/oxide interface, and the PMA of ferromagnetic/oxide heterogeneous structure is closely related to the interface orbit configuration.…”