Magnetic and Structural Properties of A-Site Ordered Chromium Spinel Sulfides: Alternating Antiferromagnetic and Ferromagnetic Interactions in the Breathing Pyrochlore Lattice

Abstract

We report a comprehensive study on the magnetic and structural properties of the spinel sulfides LiInCr 4 S 8 , LiGaCr 4 S 8 , and CuInCr 4 S 8 , where Li + /Cu + and Ga 3+ /In 3+ ions form a zinc-blende-type order. On the basis of synchrotron X-ray diffraction and magnetization data obtained using polycrystalline samples, these three sulfides are suggested to be breathing pyrochlore magnets with alternating antiferromagnetic and ferromagnetic interactions on the small and large tetrahedra, respectively. The measured magnetization processes of the three sulfides up to 72 T are significantly different. The magnetization curves of LiInCr 4 S 8 and CuInCr 4 S 8 have large hysteresis loops with different shapes, while there is no hysteresis in that of LiGaCr 4 S 8 . Geometrical frustration of the small tetrahedron is likely to give rise to a wide variety of ground states, indicating the rich physics in these antiferromagnetic-ferromagnetic breathing pyrochlore magnets. CrGa/In Li/Cu S (a) J (b) Cr J' d d'

Breathing chromium spinels: a showcase for a variety of pyrochlore Heisenberg Hamiltonians

“…Interestingly, the fact that the experimentally determined Curie-Weiss temperature of LiGaCr 4 S 8 is small is thus readily explained by a cancellation of ferromagnetic J and J by antiferromagnetic J 2 and J 3a , J 3b couplings rather than by opposite signs of J and J as hypothesized in Ref. 16. Opposite signs of J and J are only found for CuInCr 4 S 8 .…”

“…In this context, the disorder-free so-called breathing chromium spinels, which define a fairly broad range of materials (e.g. LiInCr 4 (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16), constitute a significant opportunity for carrying out the above research program in and below the O(10 2 ) K temperature scale.…”

Progress of Research in Negative Thermal Expansion Materials: Paradigm Shift in the Control of Thermal Expansion

“…Actually, NTE is known to appear in the T range of several tens of degrees on the high T side of the magnetic transition with a compound having a certain spinel or breathing pyrochlore structure (Hemberger et al, 2007; Okamoto et al, 2018; Pokharel et al, 2018). In these materials, NTE disappears below the critical temperature at which the magnetic long-range order is formed.…”

Behavior of the breathing pyrochlore lattice Ba3Yb2Zn5O11 in applied magnetic field

“…Breathing pyrochlore lattice materials have recently emerged as an interesting route to study various aspects of frustrated magnetism [1][2][3][4][5][6][7][8][9][10][11]. Examples include the potentially enhanced stability of quantum spin ice state [10], as well as the appearance of a "Weyl magnon", a bosonic analog of a Weyl fermion [12][13][14], which hosts the associated magnon arc surface states [12].…”