Low Temperature Piezomagnetism on UO2
Uranium dioxide is, by far, the most thoroughly studied actinide material and it is a key component in nuclear energy applications. Its elastic and magnetic properties, however, remain an unsolved puzzle resulting from the intertwining of magnetic interactions among U-atoms and dynamic Jahn-Teller distortions of O-atoms . In this opportunity I will discuss magnetostriction data taken in the low temperature paramagnetic and antiferromagnetic states to magnetic fields in excess of 90T at the National High Magnetic Field Laboratory. I will show that its linear magnetostriction in the antiferromagnetic state makes UO2 a piezomagnet, confirming a thirty-year-old prediction [2, 3]. During the course of this research we also found that antiferromagnetic domains in UO2 show persistent magnetoelastic memory that require external magnetic fields in excess of 18 T to be aligned, a formidable resilience to external magnetic fields 10x larger than in other known piezomagnets . The unusually strong correlations between the magnetic moments in U-atoms and lattice distortions are a direct consequence of the non-collinear symmetry of the magnetic state, and could have consequences in the thermophysical properties of this technologically important material .
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