Spin-liquid behavior inJeff=12triangular lattice compound Ba3IrTi

Abstract

Ba3IrTi2O9 crystallizes in a hexagonal structure consisting of a layered triangular arrangement of Ir 4+ (J ef f = 1/2). Magnetic susceptibility and heat capacity data show no magnetic ordering down to 0.35 K inspite of a strong magnetic coupling as evidenced by a large Curie-Weiss temperature θCW ∼ −130 K. The magnetic heat capacity follows a power law at low temperature. Our measurements suggest that Ba3IrTi2O9 is a 5d, Ir-based (J ef f = 1/2), quantum spin liquid on a 2D triangular lattice. [2] in geometrically frustrated magnets. In such materials, incompatibility of local interactions, called frustration, leads to a strong enhancement of quantum spin fluctuations and effectively suppresses the long range magnetic ordering. As a result, the material remains paramagnetic down to very low temperature compared to the Curie-Weiss (CW) temperature θ CW . The frustration in these materials often arises from some special geometries like triangular, kagomé, pyrochlore, garnet etc.[3].

Ba3MxTi3−xO9(M=Ir

“…The experimental signatures of the QSL state have been suggested to be (i) a Curie-Weiss susceptibility [C/(T − θ )] with a negative θ , (ii) no indication of spin ordering or spin freezing such as a peak in the temperature dependence of susceptibility or the presence of a bifurcation in the field cooled and zero-field cooled susceptibility below some temperature or perhaps a large "frustration ratio" f = |θ/T N |, where T N is the ordering temperature, (iii) absence of a peak in the temperature dependence of heat capacity but the presence of a magnetic contribution to the heat capacity with a power law behavior in temperature, etc. While 3d-based TMOs include several materials with QSL [3] [4] and Ba 3 YIr 2 O 9 (HP phase) [5], to our knowledge, Na 4 Ir 3 O 8 [6] was the only reported QSL among 5d-based TMOs. However, it appears that, no such dynamically disordered ground state manifold has been realized so far in 4d-based TMOs, where U and SOC are expected to be of comparable strengths.…”

“…194). The refined unit cell parameters at 300 K ({a,c} = {5.7197 (2) [4]. The refined crystal structure parameters are listed in Table I.…”

“…The Ba 3 MX 2 O 9 series with M = Co, Ni, Cu, Ru, Ir and X= Sb, Ti, [4,[11][12][13][14] displays a variety of ground states depending upon the electronic states of the ions, strength of the SOC, and the crystal-field energy. However, Ba 3 ZnIr 2 O 9 , where Ir is in the pentavalent oxidation state, shows a spinorbital liquid state because of the comparable energy scales induced by the SOC and superexchange interactions [15].…”

“…However, Ba 3 ZnIr 2 O 9 , where Ir is in the pentavalent oxidation state, shows a spinorbital liquid state because of the comparable energy scales induced by the SOC and superexchange interactions [15]. Dey et al [4] studied a J eff = 1/2 two-dimensional (2D) Mott insulator Ba 3 IrTi 2 O 9 , which has significant Ir/Ti site disorder resulting in an effective dilution of the magnetic Ir 4+ planes. Nevertheless, it appears to be an example of a spin-orbit driven spin liquid, which does not order down to 0.35 K inspite of a large antiferromagnetic Curie-Weiss temperature θ CW (∼−107 K).…”

“…In this space group, Ir 4+ (5d 5 , J eff = 1/2) and Ti 4+ (S = 0) occupy the 2b sites and form structural dimers (along the c direction) which then form triangular biplanes (ab plane) with an ordered arrangement of Ir and Ti. Between successive biplanes there is a nonmagnetic triangular layer of Ti-atoms at the 2a sites [4]. Due to their similar ionic radii, however, it is inevitable to have mixing among Ir 4+ and Ti 4+ site occupancies and Rietveld refinement carried out on x-ray data suggested this intersite disorder.…”