In the Magnetic Material and Functional Oxides department at ICMAB, the activities of the Crystallography of Magnetic and Electronic Oxides and Surfaces group are addressed to explore, understand and develop new strongly correlated materials of interest in fundamental Condensed Matter research and as novel materials for the Information technologies.
The activities of the group are based on the application of chemical and magnetic crystallography methods to the investigation of emergent functional oxides. Combining an intensive use of Large Scale Facilities (such as neutron and synchrotron sources) with symmetry analysis methodologies, we investigate the symmetry-properties relationship associated to structural, magnetic or electronic orders in functional oxides.
Current research lines include the study of structure-properties relationship in new magnetic, multiferroic and magnetoelectric materials with special charge, spin or electronic orders, and the study of novel oxides with giant responses for technological applications. In addition to bulk materials and films, surface diffraction synchrotron techniques and surface characterization methods are also applied to the study of ordering related phenomena in low-dim systems.
The neutron scattering in the field of magnetic and electronic materials presents extraordinary importance. To probe magnetic properties on atomic scale, neutron diffraction is an established technique and a unique method of choice, which allows perfect quantitative data interpretation. The magnetic moment of the neutron makes it a unique probe for magnetic properties in condensed matter on atomic scale. It gives a direct access to the spin and orbital distribution in the unit cell. In particular, magnetic structure determination is the foyer to the understanding of many fundamental phenomena in Condensed Matter research. Neutron and synchrotron techniques can be applied to investigate spin-state transitions, charge and orbital ordering, giant magneto-resistance, magnetoelectric materials as well as other emergent phenomena in frustrated materials such as spin ice, spin liquid behavior or other promising topological defects.
Multiferroics are important functional materials featuring strongly coupled order parameters that can be manipulated by external fields. Magnetoelectric multiferroics are receiving enormous attention as they open the road to new forms of multifunctional devices. However, they challenge our fundamental understanding of magnetic and ferroelectric order because a strong magnetoelectric coupling is incompatible with traditional mechanisms of ferroelectricity. The recent discovery of a new class of materials (type-II multiferroics) in which the magnetic and electric properties are strongly coupled is attracting very much interest because of the possibility to manipulate magnetism and spins by electric fields and vice-versa, to magnetically control electric charges. Future applications in information technology require new multiferroic materials fulfilling all technological requirements. Along with its technological functionalities, multiferroics are also of great interest in fundamental research into strongly correlated oxides and quantum matter.
Cobalt oxides present a plethora of very interesting properties like metal-insulator transitions, spin-state changes, giant magnetoresistance, double-exchange, phase separation, high thermoelectric power, oxygen diffusivity, mixed-conduction, charge and orbital ordering or superconductivity among others. These properties are interesting not only from a fundamental point of view but also due to their potential applicability in different fields. One very remarkable characteristic of many cobalt compounds is the ability of Co ions to adopt different spin states. This makes that Co oxides have, in comparison with other transition metal oxides, an extra degree of freedom: the spin state of Co. So, the investigation of novel cobaltites with different structures and prepared in different forms is between the most attractive opportunities within strongly correlated systems: the spin state of Co at selected sites in the structure plays a key role in the structural, magnetic, magnetotransport properties, electronic and ion mobility or the thermoelectric power. This research is inscribed inside the wider objective of understand and control the spin state and electronics degrees of freedom of Co cations, especially with 3+ valence. Trivalent cobalt oxides exhibit unique electronic phases characterized by the interplay between nearly degenerate spin states.