Research topics

Magnetocaloric Effect and materials. The magnetocaloric effect (MCE) of the materials is manifested both in the form of an isothermal entropy change and as a variation of the adiabatic temperature following the application of a magnetic field. Applications of MCE are in energy conversion: magnetic refrigeration and thermo-magnetic generators. Studied materials are Ni-Mn-X Heusler alloys.
 

Magneto-electric multiferroic materials. Class of materials showing the coexistence of two ferroic orders: ferroelectricity and ferromagnetism. Applications in multifunctional devices with crossed electrical and magnetic control (sensors, spintronics). Studied materials are AMnO3 manganites with perovskite structure.

From chiral magnets to superconductors
Many competing orders: MnSi, MnGe, MnP are helimagnets: their spin structure winds like a spiral. MnP can be be turned into superconductor by applyimg pressure.
MnSi is the prototype skyrmion lattice material: it hosts curls of spins that may be addressed as nanoscopic bits. We investigate these complex materials by muon spectroscopy, NMR and ab-initio calculations.
(see e.g.  PhysRevB.93.180509, Phys. Rev. B 97, 174414)

Ferroic and Multiferroic nanomaterials (M.Ghidini)

We combine local and global measurement techniques to study the unique functional properties that arise in nanosized ferroic and multiferroic materials.

Key publications

M. Ghidini, R. Mansell, F. Maccherozzi, X. Moya, L. C. Phillips, W. Yan, D. Pesquera,  C. H. W. Barnes, R. P. Cowburn, J.-M. Hu, S. S. Dhesi and N. D. Mathur
Shear-strain mediated magnetoelectric effects revealed by imaging
Nature Mater., 18, 840 (2019)

D. Pesquera, E. Khestanova, M. Ghidini, S. Zhang, A. P. Rooney, F. Maccherozzi, P. Riego, S. Farokhipoor, J. Kim, X. Moya, M. E. Vickers, N. A. Stelmashenko, S. J. Haigh, S. S. Dhesi and N. D. Mathur,
Large magnetoelectric coupling in multiferroic oxide heterostructures assembled via epitaxial lift-off
Nature Comm., 11, 3190 (2020)

M. Ghidini, R. Mansell, R. Pellicelli, D. Pesquera, B. Nair, X. Moya, S. Farokhipoor, F. Maccherozzi, C. H. W. Barnes, R. P. Cowburn, S. S. Dhesi and N.D. Mathur
Voltage-driven annihilation and creation of magnetic vortex states by ferroelectric domain switching 
Nanoscale 12, 5652 (2020)

M. Ghidini et al. 
XPEEM and MFM imaging of ferroic materials 
Adv. Electron. Mater. 8, 2200162 (2022)
 

Fig. 1 Visualization of complex magnetic microstructures. All images are based on XMCD-PEEM vector maps of magnetization that combine two XMCD-PEEM images obtained with orthogonal IP projections of the grazing-incidence beam (red and green arrows). a) XMCD-PEEM vector map of magnetization for a La0.7Sr0.3MnO3 film that was grown epitaxially and transferred to an electroactive substrate on which it does not grow well. Color wheel identifies the direction of local magnetization. b) Difference image obtained
by subtracting XMCD-PEEM vector maps of a polycrystalline Ni film before and after ferroelectric domain switching in its electroactive substrate. Color wheel identifies changes in the direction of local magnetization. c) The magnitude of the XMCD asymmetry for an XMCD-PEEM vector map of an La0.7Ca0.3MnO3 film on a BTO substrate, at 210 K. Red contours enclose black regions that are considered to possess zero magnetization within error. 
From Ghidini et al., XPEEM and MFM imaging of ferroic materials, Adv. Electron. Mater. 8, 2200162 (2022)