In 2023, the prize has been awarded to Otto Mustonen from the University of Birmingham for his work on the design, synthesis, and investigation of unique realisations of long-sought models of quantum magnetism using neutron diffraction and spectroscopy and muon spin relaxation techniques.

Across many of his outstanding publications he has exploited his deep understanding of the different roles of filled and empty d-orbitals to stabilise a range of novel magnetic states. He uses this understanding to develop crystal-chemical modifications to structure and magnetic interactions and this has allowed him to access new physical behaviours.

“What makes Otto an especially deserving recipient of the BTM Willis Prize is that he also uses the toolkit of neutron scattering and complementary techniques – particularly muon spectroscopy – to uncover the physics of the materials he has discovered," adds Dr Lucy Clark from the University of Birmingham. “This includes both magnetic neutron diffraction and spectroscopy, leading to a rigorous materials understanding, which is highlighted in Otto's interdisciplinary publications."

During his PhD studies, his use of inelastic neutron scattering and muon relaxation measurements to study spin waves and the elimination of magnetic order to form a spin-liquid state resulted in some of ISIS's most 'talked about' science of 2018.

Now based at the University of Birmingham, Otto's personal research focuses on exploring the generation of quantum criticality in magnetic oxides, using a range of additional advanced neutron scattering techniques, with the aim of developing design principles for crystal engineering.

While much work had been done previously substituting magnetic cations with the aim of driving quantum criticality, Otto's was the first demonstration of how a nonmagnetic ion could be used to modify the magnetic exchange to control the magnetic ground state in double perovskites. Moreover, the simple rules established for these magnetic interactions make it possible to predict the magnetic ground state of new double perovskites. This has been recognised internationally as being important, with multiple groups working on this.

“Multiple neutron scattering techniques underpin all of these studies and it was Otto's contribution of planning, performing and understanding the inelastic and polarised neutron scattering experiments that led to the key insights," said Professor Eddie Cussen, from the University of Sheffield. “It is a measure of both Otto's drive and the esteem in which he is held that the collaborations that underpin these experiments were put in place by him. His elegant application of this range of neutron techniques and the quality of his scientific discoveries makes him a highly meritorious recipient of the Willis prize."

ISIS beamline scientist Dr Helen Walker, also supported Otto's nomination, adding: “I have seen him develop from a keen and enthusiastic PhD student to a highly productive and independent investigator, who I am proud to collaborate with."

The BTM Willis prize is named in honour of Professor Terry Willis – founder of the UK Neutron Scattering Group. The prize is awarded annually to an early career researcher in recognition of a single outstanding piece of work, or a longer-term coherent body of work, in the application of neutron scattering to a significant problem in physics, chemistry, materials science, earth science, the life sciences, or engineering, or alternatively in recognition of a major development in neutron scattering instrumentation or techniques.