Laboratoire National des Champs Magnétiques Pulsés CNRS – INSA

In order to quantitatively describe the effect outlined above we have performed comprehensive mean field
calculations of the magnetoelastic distortion of TbVO4 as a function of the strength and direction of the
externally applied magnetic field [4]. The applied magnetic field was found to influence both the magnitude of
the order parameter, as observed in the splitting of the (311)/(131) and (202)/(022) pairs of Bragg peaks, and the
relative domain populations, reflected in the intensity ratio between the partners of a pair. Although the observed
splitting followed the predicted spectra, the degree of splitting was lower than expected. Various theories to
explain the quantitative difference have been proposed, one being sample heating due to the magnetocaloric
effect.
[1] P. Frings, J. Vanacken, C. Detlefs, F. Duc, J. E. Lorenzo, M. Nardone, J. Billette, A. Zitouni, W. Bras and G. L. J. A.
Rikken, Rev. Sci. Instrum. 77, 063903 (2006).
[2] G. A. Gehring and K. A. Gehring, Rep. Prog. Phys. 38, 1 (1975).
[3] A. A. Demidov and N. P. Kolmakova, Physica B 363, 245 (2005).
[4] C. Detlefs, F. Duc, Z. A. Kazeĭ, J. Vanacken, P. Frings, W. Bras, J. E. Lorenzo, P. C. Canfield and G. L. J. A. Rikken,
Phys. Rev. Lett. 100, 056405 (2008).
Magnetic field induced structural transition in the electron-doped manganite Ca0.8Sm0.16Nd0.04MnO3
The physical properties of manganite compounds, R1-xDxMnO3 (R = rare-earth La, Nd, Sm; D = alkaline-earth
metals Sr, Ca, Ba,...), such as colossal magnetoresistance (CMR) effect, charge ordering, orbital ordering and
phase separation have been extensively studied during the last ten years. One of the main results of manganite
investigation is the discovery of tendencies toward inhomogeneous states, both in experiments and simulation
models [1]. The colossal magnetoresistance effect appears to be closely linked to these mixed phase tendencies
and to the coexistence of a strong competition between the ferromagnetic (FM) metallic state and the insulating
antiferrromagnetic (AF) charge and orbital orders.
In the present work, we have been interested to investigate the structural and magnetic phase separation aspects
in the electron-doped manganite Ca0.8Sm0.16Nd0.04MnO3 [2] using our 30 T pulsed field synchrotron X-ray
powder diffraction set-up, combined with resistivity and magnetization measurements. X-ray experiments were
performed on ID20 at the ESRF whereas the resistivity and magnetization measurements were carried out at the
Institute for Nanoscale Physics and Chemistry (INPAC) in Leuven.
Upon lowering the temperature through 113 K, Ca 0.8Sm 0.16Nd 0.04MnO 3 exhibits a first order structural and
magnetic transition, associated with a metal-insulator transition. Below 125 K, both low field magnetization data
and zero field synchrotron powder diffraction showed the coexistence and competition of two magnetic and
structural phases: a major AF monoclinic state and a minor FM orthorhombic one.
Furthermore, high field X-ray and magnetization measurements at low temperature clearly revealed a field
induced structural change (from a monoclinic to an orthorhombic phase, fig. 2 and 3) associated with a
metamagnetic transition.
Fig. 2: Synchrotron X-ray powder diffraction patterns of
Ca0.8Sm0.16Nd0.04MnO3 at T = 7 K obtained for different
magnetic fields.
35
Fig. 3: Low temperature field dependence of the
monoclinic phase fraction.
[1] E. Dagotto, T. Hotta. and A. .Moreo, Physics Reports-Review Section of Physics Letters 344, 1 (2001).
[2] D. A. Filippov, K. V. Klimov, R. Z. Levitin, A. N. Vasil’ev, T. N. Voloshok, and R. Suryanarayanan, J. Phys.: Condens.
Matter 15, 8351 (2003).