Abstract
Frustrated magnetic systems exhibit extraordinary physical properties, but quantification of their magnetic correlations poses a serious challenge to experiment and theory. Current insight into frustrated magnetic correlations relies on modelling techniques such as reverse Monte-Carlo methods, which require knowledge about the exact ordered atomic structure. Here, we present a method for direct reconstruction of magnetic correlations in frustrated magnets by three-dimensional difference pair distribution function analysis of neutron total scattering data. The methodology is applied to the disordered frustrated magnet bixbyite, (Mn1-x Fe x )2O3, which reveals nearest-neighbor antiferromagnetic correlations for the metal sites up to a range of approximately 15 Å. Importantly, this technique allows for magnetic correlations to be determined directly from the experimental data without any assumption about the atomic structure.
Highlights
A perfect crystal is a three-dimensional object with complete long-range atomic order
Crystals containing magnetic atoms give rise to macroscopic magnetic properties, and magnetic materials are essential to the function of modern society, being used extensively for information storage, electricity generation and in motors
Advanced technologies will require more complex and even exotic magnetic phenomena, where atomically ordered materials do not possess long-range magnetic ordering. These disordered or frustrated magnetic materials include spinglasses (Lee et al, 1996, 2002; Paddison et al, 2016), spinliquids (Banerjee et al, 2016, 2017), spin ice (Fennell et al, 2009; Morris et al, 2009), superconductors (Glasbrenner et al, 2015; Tranquada et al, 1996) and multiferroics (Jang et al, 2017; Kalinin, 2017; Zhou et al, 2007). Such materials only contain local short-range correlations in their magnetic structures; this makes it impossible to apply conventional experimental methods such as neutron diffraction, which is commonly used for studying long-range magnetism
Summary
A perfect crystal is a three-dimensional object with complete long-range atomic order. A model crystal is built and its structure is refined to obtain a good match between the calculated scattering pattern and the experimental data Another recent approach has been the application of magnetic pair distribution function (mPDF) analysis for powder neutron scattering (Frandsen et al, 2014; Frandsen & Billinge, 2015). Such analysis gives a one-dimensional representation of the pairwise magnetic interactions, both ordered and disordered. Since it does not rely on a priori information about the atomic structure, it allows studies of magnetism in both atomically and magnetically disordered materials, and the combination of these may lead to the discovery of extraordinary new physical phenomena
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