Negative magnetothermal resistance in a disordered two-dimensional antiferromagnet

We demonstrate that a weak external magnetic field can induce negativemagnetothermal resistance for magnons in a disordered two-dimensional antiferromagnet. We study the main effect of a weak external magnetic field on the longitudinal thermal conductivity k(xx) for a disordered antiferromagnet using the weak-localization theory for magnons. We show that the weak-localization correction term of k(xx) positively increases with increasing the magnetic field parallel to the ordered spins. Since this increase corresponds to a decrease of the thermal resistivity, this phenomenon is negative magnetothermal resistance for magnons. This negative magnetothermal resistance and the weak localization of magnons will be used to control the magnon thermal current in antiferromagnetic spintronics devices. We also discuss several implications for further experimental and theoretical studies for disordered magnets.