Double phase transition in the triangular antiferromagnet Ba₃CoTa₂O₉

Abstract

Here, we report the synthesis and magnetic properties of a new triangular lattice antiferromagnet BaCoTaO. The effective spin of Co is found to be J = 1/2 at low temperatures due to the combined effect of crystal field and spin-orbit coupling. BaCoTaO undergoes two successive magnetic phase transitions at [Formula: see text] K and [Formula: see text] K in zero applied field, which is typical for triangular antiferromagnets with the easy-axis magnetic anisotropy. With increasing field, the transition anomalies are found to shift toward low temperatures, confirming the antiferromagnetic nature of the transitions. At higher fields, the transition peaks in the heat capacity data disappear and give way to a broad maximum, which can be ascribed to a Schottky anomaly due to the Zeeman splitting of spin levels. The H - T phase diagram of the compound shows three distinct phases. The possible nature of these phases is discussed.

Six-loop ε expansion study of three-dimensional O(n)×O(m) spin models

“…Values of ∆n are determined by final six-loop estimate of n + (2, 3) and the value of n we want to consider. As was found in previous section n + (2, 3) = 5.96 (19). Thus the interesting values of n for our consideration are n = 6, 7, .…”

“…Analysis of a + (2, 4 − ε) expansion within Padé approximant approach gives n + (2, 3) = 6.15 (19) while analogous treatment of the series for inverse a + (2, 4 − ε)…”

“…As in the case m = 2 we illustrate all the numerical estimates and their accuracy in Figure 3. The final estimate resulting from the data obtained is n + (3, 3) = 9.32 (19). Previous field-theoretical estimates extracted from five-loop ε expansion and found within six-loop 3D RG analysis are 9.5(5) [38] In this subsection we present, without details, numerical estimates of n + (m, 3), n − (m, 3), and n H (m, 3) for all mentioned values of m including already considered.…”

“…There are many experimental works dedicated to the frustrated spin systems where they were studied by means of optical second-harmonic spectroscopy, measurements of magnetization, susceptibility and specific heat, resistivity measurements, synchrotron X-rays and neutron diffraction, Mössbauer technique etc. [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23]. The results of these experiments turn out to be rather contradictory.…”

Spin liquids in geometrically perfect triangular antiferromagnets

“…Best material prototypes of Co-based triangular antiferromagnets are found among hexagonal perovskites of the 6H-Ba 3 CoX 2 O 9 family with X = Sb [65][66][67], Nb [68,69], and Ta [70,71] (Fig. 3a).…”