16 research outputs found

    Order from structural disorder in XYXY pyrochlore antiferromagnet Er2Ti2O7\rm Er_2Ti_2O_7

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    Effect of structural disorder is investigated for an XYXY pyrochlore antiferromagnet with continuous degeneracy of classical ground states. Two types of disorder, vacancies and weakly fluctuating exchange bonds, lift degeneracy selecting the same subset of classical ground states. Analytic and numerical results demonstrate that such an "order by structural disorder" mechanism competes with the effect of thermal and quantum fluctuations. Our theory predicts that a small amount of nonmagnetic impurities in Er2Ti2O7\rm{Er_2Ti_2O_7} will stabilize the coplanar ψ3\psi_3 (mx2y2m_{x^2-y^2}) magnetic structure as opposed to the ψ2\psi_2 (m3z2r2m_{3z^2-r^2}) state found in pure material

    Low-field behavior of an XY pyrochlore antiferromagnet: emergent clock anisotropies

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    Using Er2Ti2O7\rm Er_2Ti_2O_7 as a motivation, we investigate finite-field properties of XYXY pyrochlore antiferromagnets. In addition to a fluctuation-induced six-fold anisotropy present in zero field, an external magnetic field induces a combination of two-, three-, and six-fold clock terms as a function of its orientation providing for a rich and controllable magnetothermodynamics. For Er2Ti2O7\rm Er_2Ti_2O_7, we predict a new phase transition for H[001]{\bf H}\parallel [001]. Re-entrant transitions are also found for H[111]{\bf H}\parallel [111]. We extend these results to the whole family the XYXY pyrochlore antiferromagnets and show that presence and number of low-field transitions for different orientations can be used for locating a given material in the parameter space of anisotropic pyrochlores. Finite-temperature classical Monte Carlo simulations serve to confirm and illustrate these analytic predictions.Comment: 11 pages, accepted version with supplemental materia

    Triangular Antiferromagnet with Nonmagnetic Impurities

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    Order from structural disorder in the X

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    Low-field behavior of an X

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