Programul Naţional de Cercetare-

Electronic phases and transport mechanisms in (Ln,Ln’)_1-xA_xMn_1-yM_yO_3+d

(Ln, Ln’= rare earth, A=Sr, Ca, Ba, Pb, K; M=Cu, Cr, Co, V, Sc)

Contract No. 84/2006

Activities:

Stage I

Accomplish of the bibliographic search concerning CMR, electronic and crystalline phase composition of the magnetoresistive manganites,
Selection of some manganites with (Ln,Ln’)_1-xA_xMn_1-yM_yO_3±_d (Ln,Ln’=rare earth, A=Sr,Ca,Ba, M=Cu,Co) composition, of the temperature and the atmosphere of sintering,
Synthesis of some LL’AMnMO manganites,
Establish of the influence of the sintering conditions on the contribution of the intrinsic and extrinsic magnetoresistance
Structural characterization of bulk samples obtained by sol –gel method,
Synthesis of the data as scientific works (papers sended to be published or communicated to the national and international conferences.

Stage II

Sintering of some LL’AMnMO (M=Cu, Co) manganites with alkali oxidic additives to improve the synthesis conditions, structural characterization of bulk and thin solid films samples by X-ray diffraction and optic / electronic microscopy,
Determination of magnetic phase concentration from the dependence of specific magnetization to the temperature and Mn³⁺/Mn⁴⁺ concentration,
Determination of the magnetoresistace of bulk and thin solid films vs. temperatures and magnetic field (T = 77-500 K, H = 0-2.2 T),
Comparative study of the structural, magnetic and magnetoresistive characteristics of the samples obtained by sol-gel / ceramic methods and other specific methods for the thin solid films.

Stage III

Determination of magnetoresistive properties and magnetization of thin solid films samples,
Determination of the ratio between extrinsic and intrinsic magnetoresistance vs. chemical composition and the oxygen concentration (oxidation degree) of the thin solid films samples,
Evaluation of the obtained XRD data using FullProf, Rietrica, Dicvol, CeckCell programs,
Determination of electronic and crystalline phase concentration vs. temperature, the elaboration of some models concerning electronic and crystalline phase transformations vs. chemical composition (including Mn³⁺/Mn⁴⁺ cations ratio),
Establish the crystalline and electronic phase diagrams for the studied systems,
Establish of the mechanisms which govern the transport processes at lower/higher temperature as the transition temperature from the metallic to insulator state.

Stage IV

Sintering of some (Ln,Ln’)_1-xA_xMn_1-yM_yO₃₊_d (Ln,Ln’=rare earth, A=Sr,Ca,Ba, Pb; M=Cr, V, Sc) manganites with alkali oxidic additives to improve the synthesis,
Structural characterization of bulk and thin solid films samples by XRD (77-500K) and optic/electronic microscopy,
Determination of the magnetic properties and the magnetic phases concentration by the variation of the specific magnetization vs. temperature,
Determination of the magnetoresistance of the bulk and thin solid films vs. temperature and magnetic field (T = 77-500 K, H = 0-2.2 T),
Comparative study of the structural, magnetic and magnetoresistive characteristics of the samples obtained by ceramic, sol –gel and specific thin films methods.

Stage V

Determination of the crystalline characteristics and magnetoresistive properties of the LL’AMnMO (M = Cr, V, Sc) thin solid films samples. Magnetization measurements,
Determination of the lattice constants, of the atoms position in the unit cell, of the Mn-O distances and of the Mn-O-Mn angles, of the tolerance factors,
Evaluation of the obtained XRD data by means FullProf, Rietrica, Dicvol, CeckCell programs,
Determination of the ratio of the extrinsic and intrinsic magnetoresistance contributions vs. chemical composition and oxidation degree of the studied samples,
Determination of the crystalline and electronic phase concentration for each studied samples,
Research concerning the achievement of some magnetoresistive sensors sensible to the variation of the magnetic field / temperature, achievement of the WEB site, of a CD-ROM, of a prospect and a catalog page for the used methods and the obtained materials..

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