BEGIN:VCALENDAR VERSION:2.0 PRODID:Data::ICal 0.22 BEGIN:VEVENT DESCRIPTION:Rajesh Dutta\, Institut fur Kristallographie\, RWTH Aachen Univ ersity\n\n
Neutron scattering and its complementary X-ray scattering tec
hniques help to probe many novel and
\nexotic quantum phenomena in ma
terials and here\, two case studies on spin dynamics in square lattice
\nHeisenberg antiferromagnets (AFM) are highlighted. Doped 214 -nickelat
es have served as a model
\ncompound to understand its spin and charg
e stripe correlation in homologous superconducting
\nlayered 214 -cup
rates since last two decades. There are many similarities between La-based
and
\nPr-based 214-nickelates in terms of static stripe phases which
emerge upon doping but\, La-based
\n214 -nickelates have been treate
d so far as quassi 2D-XY AFM because of its negligible out-of-plane
\
nexchange interaction. However\, in our recent studies using inelastic neu
tron scattering (INS) and
\nlinear spin wave theory (LSWT) calculatio
ns we have observed a sizeable out-of-plane exchange
\ninteractions a
nd the corresponding 3D spin wave dispersion in Pr1.5Sr0.5NiO4 [1\, 2]. Be
sides static
\ncharge and spin stripe degrees of freedom in Pr2&minus
\;xSrxNiO4+&delta\;\, oxygen ordering on top of it plays
\nan importa
nt role and we have shown that presence of spin stripe fluctuation is not
a prerequisite
\nfor the formation of static charge stripe [3]. Anoth
er model compound multiferroic Ba2CoGe2O7
\nserves as an upstanding p
latform to study in gernal square lattice quantum physics with (S &ge\; 1<
br />\n2 ) besides its unconventional metal-ligand d-p hybridization mecha
nism which is responsible for giant
\nmagnetoelectric effects. Using
INS under applied high magnetic fields\, we have demonstrated that
\n
easy-plane-type single-ion anisotropy (SIA) can be tunable under fields an
d SIA is responsible for
\nthe changes in the optical modes and uncon
ventional electromagnon modes in 3D anisotropic spin
\ndispersion [4]
.
[1] A. Maity\, R. Dutta\, and W. Paulus\, Stripe discommensura
tion and spin dynamics of half-doped Pr3/2Sr1/2NiO4\, Phys. Rev.
\nLe
tt. 124\, 147202 (2020).
\n[2] R. Dutta\, A. Maity\, A. Marsicano\, J
. R. Stewart\, M. Opel\, and W. Paulus\, Direct evidence for anisotropic t
hree-dimensional
\nmagnetic excitations in a hole-doped antiferromagn
et\, Phys. Rev. B 102\, 165130 (2020).
\n[3] A. Maity\, R. Dutta\, an
d W. Paulus\, Spin stripe fluctuations in antiferromagnetic Pr2&minus\;xSr
xNiO4+&delta\;\, Phys. Rev. B 106\,
\n024414 (2022).
\n[4] R. Du
tta\, H. Thoma\, I. Radelytskyi\, A. Schneidewind\, V. Kocsis\, Y. Tokunag
a\, Y. Taguchi\, Y. Tokura\, and V. Hutanu\, Spin
\ndynamics study an
d experimental realization of tunable