Effect of divalent Ca ions substitution on structure and properties in multiferroic YbCrO3 chromites

The ytterbium orthochromate YbCrO
₃
has a strong anisotropic exchange interaction between Cr
³⁺
and Yb
³⁺
ions which makes the compound exhibits negative magnetization when magnetization-temperature curves are measured in a field-cooled mode with low applied field (100 Oe). YbCrO
₃
is a canted antiferromagnet (CAFM) below Néel temperature T
_N
=118 K. To investigate the interaction between Cr
³⁺
and Yb
³⁺
, we chose divalent Ca
²⁺
substitute for Yb
³⁺
in YbCrO
₃
. Polycrystalline samples Yb
_1-x
Ca
_x
CrO
₃
with x=0.0-0.30 were successfully prepared using standard solid-state reaction. X-ray diffraction patterns show that all the samples are in pure phase which can be indexed in orthorhombic structure belonging to space group Pbnm. DC magnetization measurements show that all compounds exhibit an antiferromagnetic transition at Neel temperature. However we can not find any significant dependencies between Néel temperature and Ca concentration x. We noted that Ca substitution have a great effect on the magnitude of magnetization (M). Below the temperature where M get to maximum magnitude (T
_max
, e.g. about 75 K for YbCrO
₃
) all compounds except YbCrO
₃
showed magnetic hysteresis, indicating Ca substitution brings in ferromagnetism.