Field dependence of the magnetic soft modes in Sr3Fe2O7
We propose to measure the field-dependence of the low-energy magnon spectrum of the helimagnet Sr3Fe2O7. The magnetic propagation vector is (q q 1) with q=0.142, which is doubly degenerate in the (effective) tetragonal symmetry, making this material an ideal candidate in which to study pseudo-Goldstone modes. These modes can only be observed once the helical order has been detwinned and only one of two allowed propagation vectors is populated, requiring cooling in a substantial magnetic field directed along the propagation vector we wish to select. Measurements can then be performed at lower fields. In a magnetically-detwinned sample, it is straightforward to separate the Goldstone modes near the favoured magnetic Bragg peak from pseudo-Goldstone modes, which we expect to find near the suppressed magnetic Bragg peak. Pseudo-Goldstone modes are crucial for the low-temperature properties, and in ZnCr2Se4 we discovered a field-driven closing of their gap leading to a quantum phase transition. We hope to find similar physics in Sr3Fe2O7.
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Darren C. Peets; Dmytro Inosov; IVANOV Alexandre; ONYKIIENKO Yevhen and PAVLOVSKII Nikolai. (2021). Field dependence of the magnetic soft modes in Sr3Fe2O7. Institut Laue-Langevin (ILL) doi:10.5291/ILL-DATA.4-01-1698
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