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Register a new userSquare-Lattice Antiferromagnet Subjected to a Magnetic Field Aligned with the Order Parameter
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Christoph Peter Hofmann
Publication date
2019
fields
Physics
and research's language is
English
Authors
Christoph P. Hofmann
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The thermal properties of antiferromagnetic films -- in particular, the square-lattice antiferromagnet -- subjected to an external magnetic field pointing into the direction of the staggered magnetization are explored. The effective field theory analysis of the free energy density is carried out to two-loop order. While the emphasis is on finite temperature, we also discuss the behavior of the magnetization and staggered magnetization at zero temperature. Our results imply that the staggered magnetization increases in presence of the magnetic field -- reminiscent of magnetic catalysis. Most remarkably, if staggered and magnetic field strength are kept fixed, the magnetization initially grows when temperature increases.
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Using systematic effective field theory, we explore the properties of antiferromagnetic films subjected to magnetic and staggered fields that are either mutually aligned or mutually orthogonal. We provide low-temperature series for the entropy density in either case up to two-loop order. Invoking staggered, uniform and sublattice magnetizations of the bipartite antiferromagnet, we investigate the subtle order-disorder phenomena in the spin arrangement, induced by temperature, magnetic and staggered fields -- some of which are quite counterintuitive. In the figures we focus on the spin-$frac{1}{2}$ square-lattice antiferromagnet, but our results are valid for any other bipartite two-dimensional lattice.
We explore the behavior of the order parameter and the magnetization of antiferromagnetic solids subjected to mutually parallel staggered and magnetic fields. The effective field theory analysis of the partition function is taken up to the two-loop level, where the magnon-magnon interaction comes into play. These interaction effects, however, are small. A phenomenon that comes rather unexpectedly is that the finite-temperature magnetization increases with temperature when the strengths of the staggered and magnetic field are held constant.
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