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Sujet de stage / Master 2 Internship

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Ultra-fast Spintronics with antiferromagnetic insulators

Contact: VIRET Michel, , michel.viret@cea.fr, +33 1 69 08 71 60
This 'stage' deals with an assesment of the properties of insulating antiferromagnets as ultra-fast spintronic components. THz spin current pulses will be launched using a femtosecond laser in order to excite the antiferromagnetic order.
Possibility of continuation in PhD: Oui
Deadline for application:26/03/2019

Full description:
Among the ordered electronic states that occur in solid-state materials, magnetism is uniquely robust, persisting to well above room temperature in a wide variety of materials. Ferromagnets are now routinely used in the field of information technology. On the other hand, antiferromagnets (AF), which compose the overwhelming majority of magnetically ordered materials, have not been considered as candidates for active elements. In these materials, the magnetic moments of atoms align in a regular pattern with neighbouring spins pointing in opposite directions. Because of their zero net moment, antiferromagnets are rather insensitive to a magnetic field and difficult to probe. Thus, their intrinsic properties, and especially AF domains formation and the mobility of their domain walls, are poorly known.
In the last few years, it has been demonstrated that metallic antiferromagnets can lead to giant-magnetoresistance effects (resulting from spin-orbit-coupling), which validates their use as “spintronic elements”. On the other hand, insulating antiferromagnets are much more common than their conducting counterparts because super-exchange interactions in insulators are mainly antiferromagnetic. Direct control of AF properties requires unpractically large magnetic fields, not commonly available in a laboratory. The recent development of the spin transfer torque effect produced by spin polarized currents provides an ideal way of generating (the equivalent of) a staggered field, ideal to control the AF order. This should allow to toggle AF domains and influence the AF dynamical properties, but this has not yet been demonstrated.
The ‘stage’ proposed here aims at assessing the potential of AF insulators in spintronics. These materials will be manipulated using pure spin currents generated through a newly discovered effect based on the ultra-fast demagnetization of an adjacent ferromagnetic layer. Both excitation and measurement will be carried out using a femtosecond laser. Ideally the stage should lead to a continuation as a PhD student.
Technics/methods used during the internship:
femtosecond laser, thin film depositions by evaporation and Pulsed Laser Deposition.

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