Abstract
The low energy excitation states in frustrated magnetic structures can generate quasiparticles that behave as if they were magnetic charges. These excited states produce, in the so-called spin-ice materials, two different peaks of specific heat at temperatures less than 1.5 K. In this paper, we consider that the first structure is caused by the formation of fluid of magnetic dipoles configured by the dumbbell model with a boson nature in consonance with that described by Witten for mesons. The second structure, wider than the first one, corresponds to a plasma state that comes from the breaking of a great number of dipoles, which provokes the appearance of free magnetic charges, which constitute a cool magnetic plasma fluid. In this paper, we determine thermodynamic analytical functions: the thermo-potential and internal energy and their respective derivative physical magnitudes: entropy, and magnetic specific heat. We obtain results in a good concordance with the experimental data, which allow us to explain the phase transitions occurred in these spin-ice materials at very low temperatures.
Highlights
At the present time, evidence of the existence of elementary particles with magnetic charges in a vacuum seems to be null both in high energy physics and in Cerenkov particles that come from outer cosmological space
Dusad et al [8] may have been inspired by the Cabrera measurements, and some other experiments in pirocholore crystals [9,10,11,12,13,14] have recovered the squid superconductivity device for detecting entities that can be defined as magnetic monopoles” since their behavior mimic those associated with the magnetic charges
These experimental results and those intuitions endorse the assignment of this spin nature to the one-body components of the excited low energy many-body states within the materials called spin-ices. The inclusion of this pseudospin character in the individual states substituting the magnetic structures in virtue of the dumbbell model allow us to obtain free energies or thermodynamic potentials using the Bose–Einstein and Fermi Dirac statistics for the individual components of the global excitation states of lowest energy. These thermodynamic potentials or Helmholtz functions lead us to results of the entropy and specific heat corresponding to these magnetic entities, which can be fitted to the experimental data obtained over the last 13 years
Summary
Evidence of the existence of elementary particles with magnetic charges in a vacuum seems to be null both in high energy physics and in Cerenkov particles that come from outer cosmological space. A theoretical model designed in 2008 [12] named the dumbbell model allows us to explain the low energy excitation states as quasi-free magnetic charges in the spin-ices These many-body states generated via increases of temperature are produced via spin-flips among contiguous tetrahedra, which constitute the well-known crystal structure of these materials [9,10,11,12,13,14,15,16,17,18,19,20,21,22,23]. The other peak, wider than the first, announces an increase in free magnetic charges, which constitute a clear magnetic plasma state with null total charge We analyze these structures of excited states by means of a pseudospin symmetry model in a certain phenomenological similarity to that existing in hadronic mesons [36]. The plasma is generated when the magnetic bosonic condensation disappears and is converted in a magnetic and cool neutral plasma state [45]
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