Magnetic Frustration in Lead Pyrochlores

Abstract

The rich phase diagrams of magnetically frustrated pyrochlores have maintained a high level of interest over the past 20 years. To experimentally explore these phase diagrams requires a means of tuning the relevant interactions. One approach to achieve this is chemical pressure, that is, varying the size of the non-magnetic cation. Here, we report on a new family of lead-based pyrochlores A${}_2$Pb${}_2$O${}_7$ (A = Pr, Nd, Gd), which we have characterized with magnetic susceptibility and specific heat. Lead is the largest known possible B-site cation for the pyrochlore lattice. Thus, these materials significantly expand the phase space of the frustrated pyrochlores. Pr${}_2$Pb${}_2$O${}_7$ has an absence of long-range magnetic order down to 400 mK and a spin ice-like heat capacity anomaly at 1.2 K. Thus, Pr${}_2$Pb${}_2$O${}_7$ is a candidate for a quantum spin ice state, despite weaker exchange. Nd${}_2$Pb${}_2$O${}_7$ transitions to a magnetically ordered state at 0.41 K. The Weiss temperature for Nd${}_2$Pb${}_2$O${}_7$ is ${\theta }_{\text{CW}}$ = $-$0.06 K, indicating close competition between ferromagnetic and antiferromagnetic interactions. Gd${}_2$Pb${}_2$O${}_7$ is a Heisenberg antiferromagnet that transitions to long-range magnetic order at 0.81 K, in spite of significant site mixing. Below its ordering transition, we find a $T^{3/2}$ heat capacity dependence in Gd${}_2$Pb${}_2$O${}_7$, confirmation of a ground state that is distinct from other gadolinium pyrochlores. These lead-based pyrochlores provide insight into the effects of weakened exchange on highly frustrated lattices and represent further realizations of several exotic magnetic ground states which can test theoretical models.

arXiv comment10 pages, 13 figures, published in PRB

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• Structural and magnetic properties of two branches of the Tripod Kagome Lattice family A${}_2$RE${}_3$Sb${}_3$O${}_{14}$ (A = Mg, Zn; RE = Pr, Nd, Gd, Tb, Dy, Ho, Er, Yb)
• Sensitivity of magnetic properties to chemical pressure in lanthanide garnets $L{n}_3{A}_2{X}_3{\text{O}}_{12}$, $Ln$ = Gd, Tb, Dy, Ho, $A$ = Ga, Sc, In, Te, $X$ = Ga, Al, Li
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• Order out of a Coulomb phase and Higgs transtion: frustrated transverse interactions of Nd2Zr2O7
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• Phase Competition in the Palmer-Chalker XY Pyrochlore Er${}_2$Pt${}_2$O${}_7$
• Relief of Frustration in the Heisenberg Pyrochlore Antiferromagnet Gd${}_2$Pt${}_2$O${}_7$
• Hierarchy of energy scales and field-tunable order by disorder in dipolar-octupolar pyrochlores
• Long-range dynamical magnetic order and spin tunneling in the cooperative paramagnetic states of the pyrochlore analogous spinel antiferromagnets CdYb2X4 (X = S, Se)
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• Spin Correlations in the Dipolar Pyrochlore Antiferromagnet Gd2Sn2O7
• Deviation from the dipole-ice model in the new spinel spin-ice candidate, MgEr${}_2$Se${}_4$
• Traversing the pyrochlore stability diagram; microwave-assisted synthesis and discovery of mixed B-site Ln${}_2$InSbO${}_7$ family
• Integer vs. half-integer spin on an approximate honeycomb lattice
• Magnetic Properties of Lithium-Containing Rare Earth Garnets Li3RE3Te2O12 (RE = Y, Pr, Nd, Sm-Lu)
• A new family of disorder-free Rare-Earth-based kagomé lattice magnets: structure and magnetic characterizations of RE3BWO9 (RE=Pr, Nd, Gd-Ho) Boratotungstates