Rare earth garnets are an exciting playground for studying the exotic magnetic properties of the frustrated hyperkagome lattice. Here we present a comprehensive study of the single ion and collective magnetic properties of the garnet Er3Ga5O12. Using inelastic neutron scattering, we find a crystal field ground state doublet for Er 3+ with strong Ising anisotropy along local [100] axes. Magnetic susceptibility and heat capacity measurements provide evidence for long-range magnetic ordering with TN = 0.8 K, and no evidence for residual entropy is found when cooling through the ordering transition. Neutron powder diffraction reveals that the ground state spin configuration corresponds to the six-sublattice, Ising antiferromagnetic state (Γ3) common to many of the rare earth garnets. Our results indicate that Er3Ga5O12 is an excellent model system for studying the complex metamagnetism expected for a multi-axis antiferromagnet.

We present a detailed magnetic study of the triangular antiferromagnet ErMgGaO4. A point charge calculation under the single ion approximation reveals a crystal field ground state doublet with a strong Ising-like behavior of the Er 3+ moment along the c axis. Magnetic susceptibility and specific heat measurements indicate no presence of magnetic transitions above 0.5 K and no evidence of residual entropy as temperature approaching zero. Zero field (ZF) µSR measurements shows no sign of static uniform or random field and longitudinal field (LF) µSR measurements exhibit persistent spin fluctuations down to our lowest temperature of 25 mK. Our results provide evidence of a quantum spin liquid state in the triangular antiferromagnet ErMgGaO4.A quantum spin liquid (QSL) is a state of matter in which spins are highly entangled and do not show magnetic order down to zero temperature [1]. QSL's are of great current interest both from a fundamental physics point of view and for possible applications in quantum computation [2]. Geometrically frustrated magnets (where competing magnetic interactions cannot be simultaneously satisfied) are excellent candidate materials for QSL behavior since magnetic order is suppressed in them by the frustration [3][4][5]. Such frustration frequently arises from antiferromagnetically coupled spins located on triangle-based lattices (stacked triangular, kagome, pyrochlore), and can lead to a highly degenerate ground state without magnetic order. The previously studied quasi-two dimensional triangular layered material YbMgGaO 4 (with YbFe 2 O 4 -type structure) has been attracting considerable interest as a potential quantum spin liquid candidate [6][7][8][9][10][11][12].YbMgGaO 4 has a Curie-Weiss temperature of ∼ -4 K but shows no sign of long-range order down to 30 mK [6,7,9,10]. Its magnetic specific heat in zero field shows a broad hump at 2.4 K instead of sharp λ-type peak which would be expected for a well-defined second order phase transition. The magnetic excitation spectra appears as a broad continuum in inelastic neutron scattering measurements, which has been taken as an evidence for a QSL state [7,10]. Particularly, the anisotropic exchange interactions between rare earth ions are found to be playing a crucial role in stabilizing such spin liquid ground state [6-10], although an alternative explanantion in terms of the random Ga/Mg site mixing has also been proposed [11]. Such exchange interactions associated with spin orbit coupling strongly depends on rare earth ions. It has also been found, particularly, in rare earth pyrochlores (R 2 B 2 O 7 with R = rare earth, B = non-magnetic cation), that the interplay of exchange couplings, dipolar interactions, and single ion anisotropy leads to spin glasses [5,13], spin liquids [14-16], spin ices [17], order-by-disorder [18, 19], magnetic moment fragmentation [20,21], and conventional long-range magnetic ordering [22]. These observations indicating different rare earth ions can result in much different ground states, motivating the sea...

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