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EMR Study of Electronic and Magnetic Ordering in Doped CaMn_{1-x,y}M_{x,y}O_3 (M = Ru, Mo) Perovskites

100%

Shames A., Auslender M., Rozenberg E., Gorodetsky G., Martin C., Maignan A.

Acta Physica Polonica A

2005

vol. 108

issue 2

235-242

X-band electron magnetic resonance measurements of polycrystalline CaMn_{1-x,y}M_{x,y}O_3 (M = Ru, 0≤x≤0.5; M = Mo, 0≤y≤0.14) samples were performed at 120 K≤ T≤540 K. The observed anomalies of electron magnetic resonance parameters correlate pretty well with the temperatures of antiferro-, ferromagnetic-like, and orbital/charge-ordering transitions in these systems and specify phase diagrams obtained by other techniques. However, a strong difference between resonant properties of Ru- and Mo-doped series is observed in both paramagnetic and magnetically ordered states. To describe such a difference, the energy bands diagrams, which comprise the deep impurity t_{2g}-like states + e_g-like conductive band for CaMn_{1-x}Ru_xO_3 and shallow impurity states + conductive band, both having e_g-like symmetry, for CaMn_{1-y}Mo_yO_3, are proposed. Specific electrons' contribution to the electron magnetic resonance line width explains concentration and temperature dependences of this parameter in the paramagnetic state in considered systems.

An NMR study of Pr_{0.5}Ca_{0.5}Mn_{1-x}Ga_xO_3 (x=0 and 0.03)

84%

Oates C., Kapusta C., Riedi P., Sikora M., Zając D., Rybicki D., Martin C., Yaicle C., Maignan A.

Acta Physica Polonica A

2004

vol. 105

issue 1-2

189-195

An NMR study of polycrystalline Pr_{0.5}Ca_{0.5}Mn_{1-x}Ga_xO_3 (x=0 and 0.03) at 3 K is presented. Zero field spin-echo spectra of the Ga doped compound consist of an overlapping ^{69,71}Ga signal at 74~MHz (hyperfine field of 5.3 T), a ^{55}Mn double exchange line at 375 MHz (35.5 T) and a weak Mn^{3+} signal between 400 and 550 MHz. Measurements in an applied field show a step-like increase in the double exchange line intensity, which corresponds to an increase in the amount of the ferromagnetic metallic phase. This coincides with a step-like feature in the bulk magnetization measurements. The effect is similar to that in the previous field dependent ^{55}Mn NMR measurements of Pr_{0.67}Ca _{0.33}MnO_3. At the demagnetized and remanent state, a variation of spin- spin relaxation time, T_2, across the ^{55}Mn line, due to the Suhl-Nakamura interaction is observed, which suggests that the ferromagnetic metallic double exchange regions, at liquid helium temperatures, are at least 4 nm in size.

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2 Acta Physica Polonica A

1 2005

1 2004

2 Maignan A.

2 Martin C.

1 Auslender M.

1 Gorodetsky G.

1 Kapusta C.

1 Oates C.

1 Riedi P.

1 Rozenberg E.

1 Rybicki D.

1 Shames A.

1 Sikora M.

1 Yaicle C.

1 Zając D.

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EMR Study of Electronic and Magnetic Ordering in Doped CaMn_{1-x,y}M_{x,y}O_3 (M = Ru, Mo) Perovskites

An NMR study of Pr_{0.5}Ca_{0.5}Mn_{1-x}Ga_xO_3 (x=0 and 0.03)