Thermal Expansion and Volume Magnetostriction in Breathing Pyrochlore Magnets LiACr₄X₈ (A = Ga, In, X = O, S)

Abstract

We report thermal expansion and magnetostriction in breathing pyrochlore magnets LiACr4X8 (A = Ga, In, X = O, S) measured by a dilatometric method on sintered samples. All four of these compounds showed a large volume contraction associated with antiferromagnetic order with decreasing temperature. Above the Neél temperature, LiGaCr4S8 showed negative thermal expansion, LiInCr4O8 showed positive thermal expansion with concave-downward temperature dependence, and LiInCr4S8 showed positive forced volume magnetostriction. All these phenomena are likely caused by the complex structure-magnetism correlation within the breathing pyrochlore structure with J and J'. These results suggested that breathing pyrochlore magnets are promising for the realization of various volumetric phenomena related to their magnetism not only in the magnetically-ordered phase but also in the paramagnetic phase.

Large magnetic-field-induced strain at the magnetic order transition in triangular antiferromagnet AgCrS2

“…16 The TN of LiInCr4S8 decreased by several K from 24 K at 5 T, and a large strain was induced by applying a magnetic field at 23 K just below TN, which is in contrast to the case of the 2p analogue LiInCr4O8. 18,34 These strains were reversible with respect to any change of the magnetic field, reflecting the phase transition between thermal equilibrium states. In contrast, the TN of AgCrS2 was insensitive to magnetic fields up to 9 T, as seen in the heat capacity data shown in Fig.…”

“…This V/V is comparable to V/V = 780 ppm in LiInCr4S8, which is one of the largest volume changes yet seen for an antiferromagnet. 18 The magnetic-field-induced strain of AgCrS2 at 42 K was not completely restored when the magnetic field was decreased to zero. In other words, the strain contained elastic (L/L)el and irreversible (L/L)th contributions, as indicated in the left panel of Fig.…”

“…These materials are spin-3/2 antiferromagnets, and show an antiferromagnetic order accompanied by a large volume change at Néel temperature of TN = 21 K and 24 K, respectively. [16][17][18] Sintered samples of these materials showed elastic strains of up to 660 _____________________________________ a) Electronic mail: yokamoto@nuap.nagoya-u.ac.jp ppm and 200 ppm at low temperatures by applying a magnetic field from 0 T to 7 T, respectively. The strain in LiInCr4S8 is isotropic, giving rise to a large volume change.…”

“…It was pointed out that the large shift of TN by applying a magnetic field and the presence of strong ferromagnetic interaction play important roles in the large strains in these Cr spinel compounds. 16,18 On the other hand, antiferromagnets with spontaneous magnetization, such as canted antiferromagnets, often show large magnetic-field-induced strains. 19,20 In this paper, we focus on magnetic-field-induced strains in ACrS2 (A = Cu, Ag, and Au).…”

Hedgehog-lattice spin texture in classical Heisenberg antiferromagnets on the breathing pyrochlore lattice

“…Breathing-pyrochlore magnets also provide examples of the spin-lattice-coupled ordering. Among so-far reported several compounds [33][34][35][36][37][38][39][40][41][42][43][44][45][46], the chromium oxides Li(Ga, In)Cr 4 O 8 [12][13][14][15][16][17][18] exhibit magnetic properties similar to those of ACr 2 O 4 . In Li(Ga, In)Cr 4 O 8 , the NN interactions on small and large tetrahedra, J and J ′ , are antiferromagnetic with different strength, where the ratio J ′ /J is estimated from the bond-length difference to be J ′ /J ∼ 0.1 and 0.6 for the In and Ga compounds, respectively [12].…”