INSTITUTO DE INVESTIGACIONES FISICAS DE MAR DEL PLATA
Unidad Ejecutora - UE
congresos y reuniones científicas
Spins vs. magnetic charges in spin ice: Monte Carlo simulations at low temperatures
PAMELA C. GURUCIAGA; RODOLFO A. BORZI
Congreso; 27th International Conference on Low Temperature Physics; 2014
Instituto de Física de Buenos Aires, CONICET - Departamento de Física, FCEN, UBA
Particles analogous to magnetic monopoles (MM) have been recently found as collective excitations of a kind of frustrated magnetic materials known as spin ices (SI). Their ground states present a degeneracy that grows exponentially with size, giving rise to a finite entropy even at 0K. A direct mapping between the spin degrees of freedom in SI and proton positions in water ice makes their residual entropies identical (thus the name of SI). Excitations of the multiple ground states are local defects in the magnetic structure, which interact approximately following a Coulomb law. They resemble non conserved magnetic charges, and hence their association with MM. The rotation of magnetic moments is equivalent to the creation, annihilation or translation of magnetic charges in a discrete lattice. How far can we extend the analogy between MM and conventional electric charges? May magnetic crystals similar to ionic crystals exist? To answer these questions we study SI systems, performing Monte Carlo simulations over both dipolar and nearest-neighbour models. The non-trivial phase diagrams we find can be understood in terms of the usual phases found in ionic systems. However, we see that the mechanism leading to charge correlations is more subtle than simple interactions between charges.