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.

10 pages, 13 figures, published in PRB

References in corpus (7)

• Definitive Evidence for Order-by-Quantum-Disorder in Er2Ti2O7
• Lightly stuffed pyrochlore structure of single-crystalline Yb2Ti2O7 grown by the optical floating zone technique
• Magnetic ordering in Gd2Sn2O7: the archetypal Heisenberg pyrochlore antiferromagnet
• Magnetic density of states at low energy in geometrically frustrated systems
• Bosonic Many-body Theory of Quantum Spin Ice
• Evidence for gapped spin-wave excitations in the frustrated Gd2Sn2O7 pyrochlore antiferromagnet from low-temperature specific heat measurements
• Incipient Ferromagnetism in Tb2Ge2O7: Application of Chemical Pressure to the Enigmatic Spin Liquid, Tb2Ti2O7

Cited by in corpus (7)

• Structural and Magnetic Investigations of Single-Crystals of the Neodymium Zirconate Pyrochlore, Nd2Zr2O7
• 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
• Magnetic properties of monoclinic lanthanide metaborates, $Ln$(BO${}_2$)${}_3$, $Ln$ = Pr, Nd, Gd, Tb
• Relief of Frustration in the Heisenberg Pyrochlore Antiferromagnet Gd${}_2$Pt${}_2$O${}_7$
• Long-range dynamical magnetic order and spin tunneling in the cooperative paramagnetic states of the pyrochlore analogous spinel antiferromagnets CdYb2X4 (X = S, Se)
• Long and short range magnetism in the frustrated double perovskite Ba2MnWO6
• A new family of disorder-free Rare-Earth-based kagomé lattice magnets: structure and magnetic characterizations of RE3BWO9 (RE=Pr, Nd, Gd-Ho) Boratotungstates