TY - JOUR
T1 - Real-space investigation of short-range magnetic correlations in fluoride pyrochlores NaCaCo 2 F7 and NaSrCo 2 F7 with magnetic pair distribution function analysis
AU - Frandsen, Benjamin A.
AU - Ross, Kate A.
AU - Krizan, Jason W.
AU - Nilsen, Gøran J.
AU - Wildes, Andrew R.
AU - Cava, Robert J.
AU - Birgeneau, Robert J.
AU - Billinge, Simon J.L.
N1 - Funding Information:
We thank Matt Tucker and Kate Page for assistance at ORNL. Work at Lawrence Berkeley National Laboratory and University of California, Berkeley was supported by the Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, of the U.S. Department of Energy (U.S. DOE) under Contract No. DE-AC02-05-CH11231 within the Quantum Materials Program (KC2202) and the Office of Basic Energy Sciences, U.S. DOE, Grant No. DE-AC03-76SF008. S.J.L.B.'s contributions to the mPDF data interpretation and writing were supported by the U.S. DOE under Contract No. DE-SC00112704. The crystal growth at Princeton University was supported by the U.S. DOE Office of Basic Energy Sciences, Grant No. DE-FG02-08ER46544. Use of the Spallation Neutron Source, Oak Ridge National Laboratory, was sponsored by the Scientific User Facilities Division, Office of Basic Energy Science, U.S. DOE. We thank the Institut Laue-Langevin for the use of its neutron instrumentation.
Publisher Copyright:
© 2017 American Physical Society.
PY - 2017/12/29
Y1 - 2017/12/29
N2 - We present time-of-flight neutron total scattering and polarized neutron scattering measurements of the magnetically frustrated compounds NaCaCo2F7 and NaSrCo2F7, which belong to a class of recently discovered pyrochlore compounds based on transition metals and fluorine. The magnetic pair distribution function (mPDF) technique is used to analyze and model the total scattering data in real space. We find that a previously proposed model of short-range XY-like correlations with a length scale of 10-15 Å, combined with nearest-neighbor collinear antiferromagnetic correlations, accurately describes the mPDF data at low temperature, confirming the magnetic ground state in these materials. This model is further verified by the polarized neutron scattering data. From an analysis of the temperature dependence of the mPDF and polarized neutron scattering data, we find that short-range correlations persist on the nearest-neighbor length scale up to 200 K, approximately two orders of magnitude higher than the spin freezing temperatures of these compounds. These results highlight the opportunity presented by these new pyrochlore compounds to study the effects of geometric frustration at relatively high temperatures, while also advancing the mPDF technique and providing an opportunity to investigate a genuinely short-range-ordered magnetic ground state directly in real space.
AB - We present time-of-flight neutron total scattering and polarized neutron scattering measurements of the magnetically frustrated compounds NaCaCo2F7 and NaSrCo2F7, which belong to a class of recently discovered pyrochlore compounds based on transition metals and fluorine. The magnetic pair distribution function (mPDF) technique is used to analyze and model the total scattering data in real space. We find that a previously proposed model of short-range XY-like correlations with a length scale of 10-15 Å, combined with nearest-neighbor collinear antiferromagnetic correlations, accurately describes the mPDF data at low temperature, confirming the magnetic ground state in these materials. This model is further verified by the polarized neutron scattering data. From an analysis of the temperature dependence of the mPDF and polarized neutron scattering data, we find that short-range correlations persist on the nearest-neighbor length scale up to 200 K, approximately two orders of magnitude higher than the spin freezing temperatures of these compounds. These results highlight the opportunity presented by these new pyrochlore compounds to study the effects of geometric frustration at relatively high temperatures, while also advancing the mPDF technique and providing an opportunity to investigate a genuinely short-range-ordered magnetic ground state directly in real space.
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U2 - 10.1103/PhysRevMaterials.1.074412
DO - 10.1103/PhysRevMaterials.1.074412
M3 - Article
AN - SCOPUS:85059619167
SN - 2475-9953
VL - 1
JO - Physical Review Materials
JF - Physical Review Materials
IS - 7
M1 - 074412
ER -