Collective and local excitations in Ba2CoTeO6 : A composite system of a spin-1/2 triangular-lattice Heisenberg antiferromagnet and a honeycomb-lattice J1−

Magnons and Spinons in $\mathrm{Ba}_2\mathrm{CoTeO}_6 $: A Composite System of Isolated Spin-$1/2$ Triangular Heisenberg-like and Frustrated Honeycomb Ising-like Antiferromagnets

“…4 (a). These exchange parameters also coincide with those estimated from the saturation field of subsystem A and the zerofield gap obtained by ESR measurements [43,44]. The further the wave vector moves away from the K point, the more rapidly the excitation energy deviates downward from the LSWT dispersion, as predicted by theory [19][20][21][22][23][24][38][39][40] and as observed in Ba 3 CoSb 2 O 9 [26,28].…”

“…w a G b w 7 d G R m + P j U 8 U J + + s x 0 E 7 E r I h A j e I N h 0 7 l q 7 y Z S N R i S s 3 w 0 j a n u P K D W f / Z f a + 0 Z F R r A K / n n R D 2 f T s P V / t K m E n M L W K 9 2 b t h + Z 0 3 V z c r r 1 K u b z A v X S l N 9 0 q l r j M e p m X l U q u l C h f q 8 F k 4 Q V t 0 w 4 F J K h N H k n y K Y H u k k 0 x v i 1 6 R i E s T U p h i a A p / S q p R y N A t u E j 4 W H D u g + 5 h 9 t W b v V x z x h j j R a I 4 W J H Q J p k 8 X f + w q f 8 j Y / 4 h H / 3 4 a p T R e N 3 g c 1 y y 3 g F O K z O u w + n t e d V K 5 3 h T / w D f A d 8 z F / B 6 H d + i s 9 r s v r x S t Z U Z 5 b 9 X x e n c 5 a R D F s T 7 + / X f l 2 L 8 n A m 9 J r m k I m k N 9 D f 6 r w y e d F 2 7 n d 1 p V L E 9 v q + x 6 h 3 G 5 x K M / a r e Q c y 0 v 5 Z n R Z p Q V f N Q 3 y B L a + J E 8 K n q 9 E C M v O 0 + n Q 3 Q T e e a n 6 F W K G 2 n P f F / L / O Y F I r / 8 7 l Z W V 9 v l x 5 X H 6 0 N l 9 a m s p n d p g e 0 B T N Y i q e 0 B I t 0 y o 1 E D e l A z q k I 8 M y V o y q U T 9 z H S j k m L v 0 1 z K a f w A t d d L h < / l a t e x i t > (a) ) = 0.30 K The excitation spectrum at T = 0.3 K can be divided into two parts, low-energy excitation ( ω < 5 meV) and high-energy excitation (5 < ω < 7 meV). In previous studies [43,44], the predominant exchange interactions were estimated as J 1.8 meV for subsystem A and J 1 4.8 and J 1 2.4 meV for subsystem B, where the exchange constants were estimated on the basis of the J 1 −J 2 honeycomb-lattice Ising antiferromagnet without XY components. Thus, we can deduce that the low-and high-energy spectra originate in subsystems A and B, respectively.…”

“…Previous magnetic and thermodynamic measurements and electron spin resonance (ESR) experiments indicated that these two subsystems are almost decoupled [43,44]. Because subsystems A and B have different energy scales [43,44], it is expected that the excitation spectra of these two subsystems will be observed separately, as shown below.…”

“…Ba 2 CoTeO 6 undergoes successive magnetic phase transitions at T N1 = 12.0 and T N2 = 3.0 K, which corre- spond to the orderings of subsystems B and A, respectively [43]. Previous magnetic and thermodynamic measurements and electron spin resonance (ESR) experiments indicated that these two subsystems are almost decoupled [43,44]. Because subsystems A and B have different energy scales [43,44], it is expected that the excitation spectra of these two subsystems will be observed separately, as shown below.…”

Development of short and long-range magnetic order in the double perovskite based frustrated triangular lattice antiferromagnet Ba$$_{2}$$MnTeO$$_{6}$$

“…For example, Ba CoTeO is a unique case of B-site ordered double perovskite, where Co ( S = 1/2) ions form two (triangular and honeycomb) subsystems. The spins on the triangular lattice behave as Heisenberg spins, while the spins on the honeycomb lattice show Ising like antiferromagnetic interactions 32 , 33 . Electron-spin resonance (ESR) and magnetization measurements show that applied magnetic field perpendicular to the easy-axis induces magnetization plateaus for both sub-lattices due to strong quantum effects of S = 1/2 spins 32 – 34 .…”