Magnetic nanopantograph in the SrCu2(BO3)2 Shastry–Sutherland lattice
Abstract
Magnetic materials having competing, i.e., frustrated, interactions
can display magnetism prolific in intricate structures, discrete
jumps, plateaus, and exotic spin states with increasing
applied magnetic fields. When the associated elastic energy cost
is not too expensive, this high potential can be enhanced by the
existence of an omnipresent magnetoelastic coupling. Here we
report experimental and theoretical evidence of a nonnegligible
magnetoelastic coupling in one of these fascinating materials,
SrCu2(BO3)2 (SCBO). First, using pulsed-field transversal and longitudinal
magnetostriction measurements we show that its physical
dimensions, indeed, mimic closely its unusually rich field-induced
magnetism. Second, using density functional-based calculations
we find that the driving force behind the magnetoelastic coupling
is the CuOCub superexchange angle that, due to the orthogonal
Cu2+ dimers acting as pantographs, can shrink significantly
(0.44%) with minute (0.01%) variations in the lattice parameters.
With this original approach we also find a reduction of ∼10% in
the intradimer exchange integral J, enough to make predictions
for the highly magnetized states and the effects of applied pressure
on SCBO