Complex perovskites derived from CaCu3Mn4O12

 The CaCu3Mn4O12 perovskite is a half-semiconducting and ferrimagnetic perovskite, with a TC = 360 K; it has been “rediscovered”  upon description of a considerable MR at low field: at room temperature MR is almost saturated for magnetic fields as low as 0.03 T. Moreover, other novel compounds of this family have surprised the scientific community, for instance LaCu3Fe4O12, recently described in Nature. Its unique feature is the presence of an internal charge transfer effect between Cu cations, a the A positions, and Fe cations, at the B sites of the perovskite.

The synthesis of this family of materials had been described, up to now, to proceed at 5-10 GPa; very recently we have prepared CaCu2.5Mn4.5O12 at moderate pressures of 2 GPa, with comparable properties to those previously reported.

Recent results of our group include: i) the preparation and study of Fe-substituted derivatives of LaCu3Mn4O12, studied by Mössbauer spectroscopy and neutron diffraction, ii) the description of ferromagnetic behaviour in the La(Cu3-xMnx)Mn4O12 oxides and iii) the preparation and full characterization of ThCu3Mn4O12.

On the other hand, we have checked that the replacement of Ca for La or other rare-earths in RCu3Mn4O12 has noticeable effects upon the increment of TC, besides observing a significant increase of the low-field MR, up to 3% at RT y 1 T. The peculiar magnetic structure of some members as TbCu3Mn4O12 has also been studied by NPD.

These results warrant the access to this family of oxides; the optimization of the MR properties and description of new derivatives are among the objectives of the present Research line.

The internal pressure of the R3+ cations upon decreasing in size along the rare-earth series, from La to Lu accounts for the observed enhancement of TC, by 50 K: the compression of the MnO6 octahedral units improves the overlapping between Mn and O orbitals, thereby promoting superexchange.

Recent Publications

Enhancement of the Curie Temperature along the Perovskite Series RCu3Mn4O12 Driven by Chemical Pressure of R3+ Cations (R = Rare Earths), Sanchez-Benitez, J, Alonso, JA, Martinez-Lope, MJ, de Andres, A, Fernandez-Diaz, MT, INORGANIC CHEMISTRY  49, 5679-5685 (2010).

Synthesis, magnetic properties, and neutron diffraction study of the complex perovskites R(Cu3-xMnx)Mn4O12 (R=Pr, Nd and x=1,2), Retuerto, M, Martinez-Lope, MJ, Sanchez-Benitez J., Garcia-Hernandez, M, Fernandez-Diaz, MT, Alonso, JA, JOURNAL OF APPLIED PHYSICS 108 (2010)

Preparation at moderate pressures, crystal and magnetic structure and magnetotransport of the ferrimagnetic CeCu3Mn4O12 perovskite, Sanchez-Benitez, J,  Martinez-Lope, MJ, Alonso, JA, JOURNAL OF APPLIED PHYSICS  107 (2010).

Crystal and magnetic structures of the complex perovskites LaCu3(Mn4-xFex)O12 with colossal magnetoresistance,  Sanchez-Benitez, J, Retuerto, M, Martinez-Lope, MJ, de la Calle, C, Fernandez-Diaz, MT, Alonso, JA, ZEITSCHRIFT FUR KRISTALLOGRAPHIE  225,  201- 208 (2010)

High-pressure preparation and characterization of new metastable oxides: the case of NdCu3Mn3MO12 (M=Fe,Cr). Sanchez-Benitez J.,Kayser P., Martinez-Lopede la Calle C., Retuerto, M., Fernandez-Diaz, MT, Alonso, JAJOURNAL OF PHYSICS: Conference Series 325, 012002 (2011).

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