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OnderzoekZernike (ZIAM)VSOPTTobey Group

Tobey Group

The group is active in the area of condensed matter physics and optical properties of materials. Using ultrafast lasers and time-resolved techniques, we study the dynamics of materials when they are perturbed from their equilibrium states. We are currently involved in studying magnetization dynamics in a range of materials including strongly correlated materials such as transition metal oxides and transition metal chalcogenides. Our methods span the entire electromagnetic spectrum from the terahertz to hard x-rays, employing both lab based lasers and large scale facilities.

Below you’ll find details of specific experiments we are currently undertaking.

Transient Grating Spectroscopy in Magnetic Materials

The transient grating (TG) technique is a well-established method for generating a spatially inhomogeneous excitation in materials. The spatial inhomogeneity allows us to monitor the motion (diffusion) of the excitation in the material in real time. In non-magnetic materials this technique is used regularly to monitor in-plane carrier and thermal diffusion in a range of materials including semiconductors, metals, and superconductors.

In magnetic materials, we can use the TG method to generate narrowband magnetoelastic waves via inverse magnetostriction – the coupling of magnetization to the acoustic strain in a material. We have recently shown that this method can be used to generate broadly tunable, narrowband, spin waves in polycrystalline nickel.

Transient grating technique
Transient grating technique

Magnetization Dynamics in Intercalated Dichalcogenides

Dichalcogenides are layered materials that exhibit a wide range of novel properties. When atoms are incorporated (intercalated) into the van der Waal’s gap, new material properties emerge including, superconductivity, and magnetism. This latter situation occurs when 3d transition metals such as Fe, Ni, Mn, and Co are intercalated between the layers.

In this project we are studying magnetization dynamics of a range of 3d intercalated materials. Using time resolved MOKE we monitor the evolution of the magnetic properties when the sample is subjected to a perturbation by light. These experiments allow us to understand how spin angular momentum is dissipated when the materials is driven out of equilibrium.

Intercalated materials
Intercalated materials

Ultrafast X-ray Scattering in Correlated Oxides

Materials with strong electronic correlations often exhibit ordered patterns of orbitals, spins, and lattice distortions. Using techniques such as time-resolved resonant soft x-ray diffraction, we can tune into a particular ordered degree of freedom and probe its evolution when driven out of equilibrium. Using time resolved techniques we can hope to understand how different degrees of freedom couple to each other by studying their temporal evolution.

In this set of measurements, we use both synchrotron and free electron sources to study the femtosecond and picosecond dynamics of charge, orbital and spin ordering in materials such as La0.5Sr1.5MnO4 and La1.875Ba0.125CuO4.

Laatst gewijzigd:25 september 2015 15:44