Real-space investigation of short-range magnetic correlations in fluoride pyrochlores NaCaCo2F7 and NaSrCo2F7 with magnetic pair distribution function analysis

In geometrically frustrated magnets the crystal lattice prevents competing magnetic interactions from being simultaneously satisfied. Consequently these materials often possess fascinating magnetic properties such as unusual short-range magnetic correlations. However, studying short-range magnetic structure has historically been a notoriously difficult experimental task. Here, Frandsen $e\phantom{\rule{0}{0ex}}t$ $a\phantom{\rule{0}{0ex}}l$. apply a new experimental technique---magnetic pair distribution function (mPDF) analysis---to uncover the local magnetic structure and temperature dependence of recently-discovered frustrated magnets NaMCo${}²$F${}⁷$ (M=Ca,Sr). The results further establish these materials as an important new class of geometrically frustrated magnets with observable frustration effects at unusually high temperatures (~200 K), while also opening the door for a plethora of future studies of frustrated magnets using the mPDF method.