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Branton Campbell in the lab

Branton J. Campbell

Professor

Department of Physics & Astronomy

Brigham Young University

Provo, UT 84602, USA

Tel: 801-422-5758, Fax: 801-422-0553

Email: branton_campbell[at]byu.edu

//physics.byu.edu/faculty/campbell/

Research Interests

I apply state-of-the-art x-ray and neutron scattering techniques to study local and long-range structures in a variety of complex solids, including fast-ion conductors, ferroelectric relaxors, high-temperature superconductors, and colossal magnetoresistive manganites, where nanoscale structural features influence macroscopic physical properties. This includes the development of symmetry-mode analysis (through the tools of the ISOTROPY Software Suite) for the determination, refinement and interpretation of distorted structures involving lattice strains, atomic displacements, magnetic moments and occupational orderings at both commensurate and incommensurate wavevectors.

Megapixel X-ray Camera

In this image of from BYU's x-ray diffraction facility, x-rays arriving from the left scatter in all directions from a tiny crystal at the center, and are then imaged by a 16-megapixel x-ray camera. The often beautiful scattering patterns that result contain a wealth of information about the atomic structure of the sample. The speed and sensitivity of state-of-the-art instruments like this have revolutionized the study of crystalline materials.

Selected Publications

A recapitulation of magnetic space groups and their UNI symbols

B. J. Campbell and H. T. Stokes (et al.)

The mathematical structure, description and classification of magnetic space groups is briefly reviewed, with special emphasis on the recently proposed notation, the so-called UNI symbols [Campbell et al. (2022). Acta Cryst. A78, 99–106]. As illustrative examples, very simple magnetic space groups from each of the four possible types are described in detail.

Guidelines for communicating commensurate magnetic structures. A report of the International Union of Crystallography Commission on Magnetic Structures

B. J. Campbell (et al.)

A report from the International Union of Crystallography Commission on Magnetic Structures outlining the recommendations for communicating commensurate magnetic structures.

Chiral multiferroicity in two-dimensional hybrid organic-inorganic perovskites

Branton J. Campbell (et al.)

Chiral multiferroics offer remarkable capabilities for controlling quantum devices at multiple levels. However, these materials are rare due to the competing requirements of long-range orders and strict symmetry constraints. In this study, we present experimental evidence that the coexistence of ferroelectric, magnetic orders, and crystallographic chirality is achievable in hybrid organic-inorganic perovskites [(R/S)-β-methylphenethylamine]2CuCl4. By employing Landau symmetry mode analysis, we investigate the interplay between chirality and ferroic orders and propose a novel mechanism for chirality transfer in hybrid systems. This mechanism involves the coupling of non-chiral distortions, characterized by defining a pseudo-scalar quantity,

(

represents the ferroelectric displacement vector and

denotes the ferro-rotational vector), which distinguishes between (R)- and (S)-chirality based on its sign. Moreover, the reversal of this descriptor’s sign can be associated with coordinated transitions in ferroelectric distortions, Jahn-Teller antiferro-distortions, and Dzyaloshinskii-Moriya vectors, indicating the mediating role of crystallographic chirality in magnetoelectric correlations.

Computational Screening and Stabilization of Boron-Substituted Type-I and Type-II Carbon Clathrates

Bryce T. Eggers and Branton J. Campbell (et al.)

Boron substitution represents a promising approach to stabilize carbon clathrate structures, but no thermodynamically stable substitution schemes have been identified for frameworks other than the type-VII (sodalite) structure type. To investigate the possibility for additional tetrahedral carbon-based clathrate networks, more than 5000 unique boron decoration schemes were investigated computationally for type-I and type-II carbon clathrates with a range of guest elements including Li, Na, K, Rb, Cs, Mg, Ca, Sr, and Ba. Density functional theory calculations were performed at 10 and 50 GPa, and the stability and impact of boron substitution were evaluated. The results indicate that the boron-substituted carbon clathrates are stabilized under high-pressure conditions. Full cage occupancies of intermediate-sized guest atoms (e.g., Na, Ca, and Sr) are the most favorable energetically. Clathrate stability is maximized when the boron atoms are substituted within the hexagonal rings of the large [5(12)6(2)]/[5(12)6(4)] cages. Several structures with favorable formation enthalpies <-200 meV/atom were predicted, and type-I Ca8B16C30 is on the convex hull at 50 GPa. This structure represents the first thermodynamically stable type-I clathrate identified and suggests that boron-substituted carbon clathrates may represent a large family of diamond-like framework materials with a range of structure types and guest/framework substitutions.

Electron Spin Decoherence Dynamics in Magnetic Manganese Hybrid Organic–Inorganic Crystals: The Effect of Lattice Dimensionality

Branton J. Campbell (et al.)

Organic–inorganic metal hybrids with their tailorable lattice dimensionality and intrinsic spin-splitting properties are interesting material platforms for spintronic applications. While the spin decoherence process is extensively studied in lead- and tin-based hybrids, these systems generally show short spin decoherence lifetimes, and their correlation with the lattice framework is still not well-understood. Herein, we synthesized magnetic manganese hybrid single crystals of (4-fluorobenzylamine)2MnCl4, ((R)-3-fluoropyrrolidinium)MnCl3, and (pyrrolidinium)2MnCl4, which represent a change in lattice dimensionality from 2D and 1D to 0D, and studied their spin decoherence processes using continuous-wave electron spin resonance spectroscopy. All manganese hybrids exhibit nanosecond-scale spin decoherence time τ2 dominated by the symmetry-directed spin exchange interaction strengths of Mn2+–Mn2+ pairs, which is much longer than lead- and tin-based metal hybrids. In contrast to the similar temperature variation laws of τ2 in 2D and 0D structures, which first increase and gradually drop afterward, the 1D structure presents a monotonous rise of τ2 with the temperatures, indicating the strong correlation of spin decoherence with the lattice rigidity of the inorganic framework. This is also rationalized on the basis that the spin decoherence is governed by the competitive contributions from motional narrowing (prolonging the τ2) and electron–phonon coupling interaction (shortening the τ2), both of which are thermally activated, with the difference that the former is more pronounced in rigid crystalline lattices.