Quasi-two-dimensional antiferromagnet on a triangular latticeRbFe(MoO4)2

Abstract

R bFe(M oO 4)2 i s a rare exam pl e of a nearl y tw o-di m ensi onal H ei senberg anti ferrom agnet on a tri angul arl atti ce. M agneti c resonance spectra and m agneti zati on curvesrevealthatthesystem hasa l ayered spi n structure w i th si x m agneti c subl atti ces. T he subl atti cesw i thi n a l ayerare arranged i n a tri angul arm annerw i th the m agneti zati on vectors120 apart. T he H T phase di agram ,contai ni ng atl east ve di erentm agneti c phasesi sconstructed. In zero el d,R bFe(M oO 4)2 undergoesa phase transi ti on atT N = 3: 8 K i nto a non-col l i near tri angul ar spi n structure w i th al lthe spi ns con ned i n the basalpl ane. T he appl i cati on ofan i n-pl ane m agneti c el d i nduces a col l i near spi n state betw een the el ds H c1= 47 kO e and H c2= 71 kO e and produces a m agneti zati on pl ateau at one-thi rd ofthe saturati on m om ent. B oth the ESR and the m agneti zati on m easurem ents al so cl earl y i ndi cate an addi ti onal rst-order phase transi ti on i n a el d of35 kO e. T he exact nature ofthi s phase transi ti on i s uncertai n.PA C S num bers: 76.50+ g;75.50.E e;75.30.C r I. IN T R O D U C T IO N

Order by Quenched Disorder in the Model Triangular Antiferromagnet RbFe(MoO4)2

“…3) have an energy gap of Δ 0 ≃ 90 GHz and for H⊥c consist of the two frequency branches, ascending and descending with an applied magnetic field in agreement with the previous results [8,24]. The ascending branch is split into two closely positioned branches (A) and (B) by the weak interplane interactions.…”

“…The frequency of the descending branch (C) is reduced almost to zero for the field approaching the lower boundary of the plateau, while another mode (D), of a higher frequency, appears near the entrance of the plateau. Modes in the middle of the plateau (E) and at the upper boundary (F) are also detected in qualitative agreement with the theory [6] and previous experiments [8]. Finally, a weakly absorbing mode (G) near 30 GHz appears due to a splitting of the zero-frequency mode [8].…”

“…A spectacular manifestation of frustration in TLAFs is the 1=3 magnetization plateau with the up-updown (uud) spin structure stabilized by fluctuations out of a degenerate manifold of classical ground states [4][5][6]. A 1=3 magnetization plateau has been experimentally observed in a number of TLAFs [7][8][9][10][11]. Generally, it is a challenging task to distinguish the pure frustration-driven plateaus from those produced by additional perturbations, such as an Ising anisotropy or magnetoelastic coupling.…”

“…The crystals of Rb 1−x K x FeðMoO 4 Þ 2 were prepared as previously described [8]. In addition to a controlled amount of K, about 1 atomic percent of Al was also found in some samples.…”

FiniteU-induced competing interactions, frustration, and quantum phase transition in a triangular-lattice antiferromagnet

“…As a recent example of quasitwo-dimensional antiferromagnetism on a triangular lattice exhibiting the 120 0 spin ordering, RbFe(MoO 4 ) 2 has been studied using elastic neutron scattering, 19 and magnetic resonance and magnetization experiments. 20 The Hubbard model on a triangular lattice has been studied recently using a variety of tools. The nonmagnetic insulating state near the Mott transition has been studied using the path integral renormalization group method, 21 in which the HF results are systematically improved to reach the true ground state by taking account of quantum fluctuations.…”