Ultrafast Optical Control of Magnetic Interactions in Carrier-Density-Controlled Ferromagnetic Semiconductors

Masakazu Matsubara

doi:10.3390/app9050948

Abstract

Investigation of the interaction of ultrashort laser pulses with magnetically ordered materials has become a fascinating research topic in modern magnetism. Especially, the control of magnetic order by sub-ps laser pulses has become a fundamentally important topic with a high potential for future spintronics applications. This paper will review the recent success in optically controlling the magnetic interactions in carrier-density-controlled ferromagnetic semiconductor EuO doped with Gd ions. When the Gd concentration is low, the magnitude of the magnetic interaction is enhanced by the irradiation of ultrashort laser pulses, whereas it is attenuated when the Gd concentration is high. In ferromagnetic Eu1−xGdxO, we thereby demonstrate the strengthening as well as the weakening of the magnetic interaction by 10% and within 3 ps by optically controlling the magnetic exchange interaction. This principle—ultrafast optical control of magnetic interaction—can be applied to future ultrafast opto-spintronics.

Highlights

Spintronics, known as spin-electronics, utilizing the spin degree of freedom in addition to the charge of electrons has attracted much attention in recent years from the viewpoint of the creation of new driving principles of electric and magnetic devices and energy conservation technology
Proportional the square the dynamics and modulation the exchange interaction can be to accessed usingofan all-optical technique dependence the magnetization applied magnetic field is extracted andwere shown in the lower study, ultrafast spin dynamics afteron thethe photoexcitation were investigated in carrier-density-controlled in
I magnetization-induced SHG (MSHG)− I MSHG the MSHG intensity normalized by the value before photoexcitation, ∆I

Summary

Introduction

Spintronics, known as spin-electronics, utilizing the spin degree of freedom in addition to the charge of electrons has attracted much attention in recent years from the viewpoint of the creation of new driving principles of electric and magnetic devices and energy conservation technology. The demand for an ever-increasing speed of manipulation in magnetic information storage has triggered a search for new methods for control of the spin functionality on the ultrafast timescale. Since the control speed of the spin by magnetic fields is already approaching its limit, how fast the spin functionality can be manipulated is one of the most important issues in modern technology. Under such circumstances, the recent development of ultrafast optical technology has opened the way to control the spin by light. The use of ultrashort optical pulses that are much shorter than the fundamental timescales such as spin-lattice relaxation or precession times allows us to excite magnetic media and to study the spin dynamics after ultrashort optical

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Discussion

Conclusion