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Magnetismus Poster: Do., 13:00–15:30 D-P238
Evolution of incommensurate magnetic order from A-type antiferromagnetism
in Nd1−xYxMnO3
Sven Landsgesell 1 , Oleksandr Prokhnenko 1 , Nadir Aliouane 1 , Dimitri
Argyriou 1
1 Hahn-Meitner-Institut Berlin GmbH (HMI), Glienicker Straße 100, 14109 Berlin
The evolution of spin- and orbital-ordered states for LnMnO3 with Ln=La - Ho has
attracted significant attention in recent years. By lowering the Mn-O-Mn bond angle
(by decreasing the ionic radius of Ln) the Neel-temperature decreases and at Ln = Tb
the A-type antiferromagnet transforms to an incommensurate (IC) spin-spiral phase
for Ln=Gd,Tb,Dy. The spin-spiral breaks both inversion and time reversal symmetry
leading to a strong coupling between magnetism and ferroelectric polarization.
In this work we study we investigate the evolution of the crystal and magnetic structure
from the A-type phase to the IC spin spiral. This was achieved by systematically doping
yttrium into NdMnO3. By that the tolerance factors can be lowered to values similar
to that for multiferroic TbMnO3. One advantage of this appoach is that the tolerance
factor can be tuned and that neodymiun and yttrium are not high neutron absopbing
elements in sharp contrast to other rare earths like Gd, Dy and Eu.
Compositions x = 0 to 0.5 in 0.1 steps have been prepared, neutron and x-ray powder
diffraction patterns were measured at room temperature and 2K while the magnetic
properties were measured with a SQUID magnetometer. It can be shown that by
decreasing the tolerance factor that way, similar effects can be seen as with varying the
ionic size of the rare earth ions. For example we found that for x = 0.4 and higher the
incommensurate phase (δ = 0.2 -> 0.25) co-exist with the A-type antiferromagnetic
phase. This suggests the transition from A-type to spin-spiral is discontinous.