Structural phase separation in La2/3Ba1/3MnO3 perovskite: Electronic structure, magnetic and ultrasound effects
E.
Fertmana, A.
Beznosova, C. Ritterb, V. Desnenkoa, P.
Pal-Vala, D. Khalyavinc
aInstitute for Low Temperature Physics and Engineering NASU, 61103,
Kharkov, Ukraine
e-mail: fertman@ilt.kharkov.ua
b Laue-Langevin, Boite Postale 156, 38042 Grenoble Cedex 9, France
cInstitute of Solid State and
Semiconductor Physics NASB, 220072, Minsk, Belarus
Recently it was revealed that the La2/3Ba1/3MnO3
CMR manganite undergoes a structural phase transformation of martensitic type
with TS≈200 K, which causes a crystal phase separation of the compound. Below
300 K the oxide represents a mixture of the high temperature rhombohedral 
(austenite)
and the low temperature orthorhombic Imma
(martensite) phases [1]. The present work shows a correlated temperature
behavior of the electronic, lattice and magnetic characteristics of La2/3Ba1/3MnO3
in the temperature range 5-370 K.
Neutron diffraction experiment showed that the electronic structure of
the compound displays strong peculiarities in the vicinity of TS: the temperature
dependences of the Mn-O-Mn bond angles of the Imma phase show discontinuities (Fig. 1, upper panel), which was
considered as an evidence of an electronic transition which affects the
structural phase transformation studied. The temperature dependent lattice distortion of both crystal phases are highest in the TS region. The crystal
structure evolution results in a peculiar behavior of the magnetic and
ultrasound properties of the compound in the TS region. The pronounced hysteretic behavior of sound
velocity v (Fig. 1, lower panel),
decrement δ and magnetization M, giant
temperature alteration of ultrasound properties, and the step-like temperature
dependence of the magnetic susceptibility of the single crystalline compound
reflect the 1st order (martensitic) nature of the structural
transformation.
