Magnetic ordering in a frustrated bow-tie lattice

Abstract

aWe report a systematic X-ray and powder neutron diffraction study of the geometrically frustrated

Phase stability of the layered oxide, Ca2Mn3O8; probing interlayer shearing at high pressure

“…Ca 2 Mn 3 O 8 was synthesised using a molten salt method as previously reported by us. 30 Briefly, stoichiometric ratios of CaCO 3 (Sigma Aldrich, Z99%), MnCO 3 (Sigma Aldrich, Z99%) and a eutectic mixture of KCl/NaCl (350% w/w) were mixed and reacted for 48 hours at 973 K followed by a second heating cycle of 24 hours at 973 K. After both heating cycles, the material was quenched to room temperature. Between heating cycles the material was washed and dried under ambient conditions and an additional 350% (w/w) eutectic mixture of KCl/NaCl was added for the second heating.…”

“…18 The Rietveld fit to the data clearly indicates an excellent fit to the monoclinic, C2/m, model expected for Ca 2 Mn 3 O 8 . 18,30,31 Additional phases of Pb (Fm% 3m) from the pressure calibrant and, ZrO 2 (P4 2 /nmc) and Al 2 O 3 (R% 3c) from the anvil were also refined.…”

“…This could possibly be related to short range magnetic correlations which are known to propagate at temperatures below approximately 130 K at ambient pressure. 30 In order to understand this further the behaviour of the individual bond lengths and polyhedra need to be understood upon compression. (Fig.…”

“…This occurs at the same temperature as a deviation from Curie-Weiss behaviour observed in magnetic susceptibility measurements and is consistent with short-range spin correlations. 30 Data collected between 300 and 1273 K show that the monoclinic structure is remarkably stable up to a temperature of approximately 1200 K before it decomposes into the perovskite, CaMnO 3 and marokite, CaMn 2 O 4 phases. 31 Moreover, electrical measurements confirm that Ca 2 Mn 3 O 8 is an electronic conductor in the temperature range, 400-700 K with an activation energy of approximately 0.50(1) eV.…”

“…30 The high crystallinity of these materials allowed us to perform more comprehensive studies of the thermal stability and magnetic behaviour of Ca 2 Mn 3 O 8 . 30,31 Low temperature studies (1.8-300 K) showed that Ca 2 Mn 3 O 8 orders antiferromagnetically with an mmkk arrangement of the magnetic spins at a Néel temperature (T N ) of approximately 58 K. 30 Additionally, an invariant behaviour below 130 K is seen in the lattice parameter, b and the monoclinic b angle. This occurs at the same temperature as a deviation from Curie-Weiss behaviour observed in magnetic susceptibility measurements and is consistent with short-range spin correlations.…”