48 research outputs found
Giant spontaneous magnetostriction in MnTe driven by a novel magnetostructural coupling mechanism
We present a comprehensive x-ray scattering study of spontaneous
magnetostriction in hexagonal MnTe, an antiferromagnetic semiconductor with a
Neel temperature of K. We observe the largest
spontaneous magnetovolume effect known for an antiferromagnet, reaching a
volume contraction of . This can be justified
semiquantitatively by considering bulk material properties, the spatial
dependence of the superexchange interaction, and the geometrical arrangement of
magnetic moments in MnTe. The highly unusual linear scaling of the
magnetovolume effect with the short-range magnetic correlations, beginning in
the paramagnetic state well above , points to a novel physical
mechanism, which we explain in terms of a trilinear coupling of the elastic
strain with superposed distinct domains of the antiferromagnetic order
parameter. This novel mechanism for coupling lattice strain to robust
short-range magnetic order casts new light on magnetostrictive phenomena and
also provides a template by which the exceptional magnetostrictive properties
of MnTe might be realized in a wide range of other functional materials.Comment: Submitted May 11, 202
Phase Diagram of KxFe2-ySe2-zSz and the Suppression of its Superconducting State by an Fe2-Se/S Tetrahedron Distortion
We report structurally tuned superconductivity in KxFe2-ySe2-zSz (0<=z<=2)
phase diagram. Superconducting Tc is suppressed as S is incorporated into the
lattice, eventually vanishing at 80% of S. The magnetic and conductivity
properties can be related to stoichiometry on poorly occupied Fe1 site and the
local environment of nearly fully occupied Fe2 site. The decreasing Tc
coincides with the increasing Fe1 occupancy and the overall increase in Fe
stoichiometry from z = 0 to z = 2. Our results indicate that the irregularity
of Fe2-Se/S tetrahedron is an important controlling parameter that can be used
to tune the ground state in the new superconductor family.Comment: 5 pages, 4 figure