Magnetism and spin dynamics of the S = 32 frustrated trillium lattice compound K2CrTi(PO4)3

Abstract

Competing magnetic interactions, frustration-driven quantum fluctuations, and spin correlations offer an ideal route for the experimental realization of emergent quantum phenomena with exotic quasiparticle excitations in three-dimensional frustrated magnets. In this context, trillium lattice, wherein magnetic ions decorate a three-dimensional chiral network of corner-shared equilateral triangular motifs, provides a viable ground. Herein, we present the crystal structure, dc and ac magnetic susceptibilities, specific heat, electron spin-resonance (ESR), muon spin-relaxation (μSR) results on the polycrystalline samples of K2CrTi(PO4)3 wherein the Cr3+ ions form a two-coupled trillium lattice. The Curie-Weiss fit of the magnetic susceptibility data above 100 K yields a Curie-Weiss temperature θCW = -23 K, which indicates the presence of dominant antiferromagnetic interactions between S=3/2 moments of Cr3+ ions. For temperatures below 40 K, the Curie-Weiss temperature is reduced to θCW = -3.5 K, indicative of the appearance of subdominant ferromagnetic interactions. The specific heat measurements reveal the occurrence of two consecutive phase transitions, at temperatures TL=4.3 K and TH=8 K, corresponding to two different magnetic phases. Additionally, it unveils the existence of short-range spin correlations above the ordering temperature TH. The power-law behavior of ESR linewidth suggests the persistence of short-range spin correlations over a relatively wide critical region (T-TH)/TH>0.25 in agreement with the specific heat results. The μSR results provide concrete evidence of two different phases corresponding to two transitions, coupled with the critical slowing down of spin fluctuations above TL and persistent spin dynamics below TL, consistent with the thermodynamic results. Moreover, the μSR results reveal the coexistence of static and dynamic local magnetic fields below TL, signifying the presence of complex magnetic phases owing to the entwining of spin correlations and competing magnetic interactions in this three-dimensional frustrated magnet. © 2024 American Physical Society.