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PHOENICS: PHOto-inducEd femtosecoNd magneto-electrIC Spin manipulation in antiferromagnets (funded by the DFG)

Principal investigators:

Summary:

Light has already demonstrated the potential to manipulate the magnetic order in solids on the femtosecond time-scale, disclosing a regime of spin dynamics which cannot be interpreted with thermodynamics. In fact, this conventional approach is based on the concept of equilibrium, which does not apply to the femtosecond time-scale. Recently it has been widely pointed out that magnetically ordered materials with no net magnetisation, i.e. antiferromagnets(AFs), are promising for spintronics. Moreover, AFs possess intrinsically faster spin dynamics in comparison with ferromagnets. Although some pioneer investigations have reported the ultrafast excitation and coherent control of the oscillatory dynamics of the order parameter in AFs (L), the ultrafast switching of L is missing. In addition, the possibility to couple the femtosecond spin dynamics to charges has not been addressed yet, although it is necessary to integrate any novel magnetic recording concept with the charge-based present-day technology.
Our project aims at overcoming these limitations investigating a magnetoelectric AF, i.e. an AF in which both time-reversal and space-inversion symmetries are broken. This property generates a plethora of effects, on which our project relies. First, a combined action of DC magnetic and electric fields reverses L by 180 degrees. We will scale this concept to the ultrafast time-scale by employing the electric field of femtosecond laser pulses. Second, a magneto-optical effect linearly proportional to L is active, as already experimentally demonstrated. Such an effect, symmetry forbidden in conventional AFs, is necessary to disentangle the two states with reversed L generated by applying electric and magnetic fields. Third, it has been predicted that due to the magnetoelectricity the spin configuration in the AF affects the spectrum of the surface plasmon polariton (SPP) of a metallic layer deposited on top of the magnetic material. We will explore this scenario on the ultrafast time-scale, assessing whether spin dynamics in the AFs can change transiently the spectrum of the SPP. This concept carries the potential to transfer coherence from the photo-induced spin dynamics to charges on the femtosecond time-scale.