ELECTRICAL AND MAGNETIC BEHAVIOR OF TRANSITION METAL OXIDES Ln_0.7A_0.3TMO₃, Ln= La, Pr; A = Ca, Sr AND TM = Mn, Co

Abstract

We present a detailed magnetic study of the polycrystalline transition metal oxides Ln 0.7 A 0.3 TMO 3, Ln = La , Pr ; A = Ca , Sr and TM = Mn , Co at low temperatures including electrical resistance, magnetization and ac susceptibility measurements. The effect of the A-site and B-site substitutions on the properties of these compounds is discussed. The results of this analysis indicate that the electrical and magnetic behavior of these compounds have some reminiscences of the manganites having similar formula, but the spin disorder and the grain boundary effects control the properties of these materials.

Low Temperature Magnetic Properties of Pr0.7(Ca,Sr)0.3CoO3Oxides

“…The shape of the M (T ) curve for this sample was rather complex, not typical for pure ferromagnets, with a maximum in M ZF C (T) at T f ∼ 16 K and a frequency dependent maximum in ac susceptibility (not shown), both in the real part χ (T ) and in the imaginary part χ (T ) [6,8]. The ferromagnetic transition temperatures increase with increasing Sr content in the samples.…”

“…The bifurcation between M ZF C (T ) and M F C (T ) curves is typical for doped cobaltites [3][4][5][6][7][8][9][10][11][12][13][14][15]16]. No saturation was seen in M (H) curves for any of the samples, even up to 12 T. Such a behavior suggests the coexistence of a dominant ferromagnetic phase together with a non-ferromagnetic one, i.e., a phase separation scenario.…”

“…The compound Pr 0.7 Sr 0.3 CoO 3 was found to be ferro- * corresponding author; e-mail: ideac@phys.ubbcluj.ro magnetic (below 170 K) and metallic down to about 100 K, and then semiconductor at lower temperatures [4][5][6]. Pr 0.7 Ca 0.3 CoO 3 has a seminconductor-like (in the whole temperature range) and a magnetic cluster-glass behavior [6][7][8][9] below 70 K. The physical properties of these compounds will depend on the average size of the A-site (Ln 3+ and A 2+ ) cations, r A = x i r i (where x i is the fractional occupancy of A-site ions, and r i is the corresponding ionic radius) [10,11].…”

Effects of Partial Manganese Substitution by Cobalt on the Physical Properties of Pr0.7Sr0.3Mn(1−x)CoxO3 (0 ≤ x ≤ 0.15) Manganites

“…While studies by I.G. Diack et al [ 28 ] in the and systems have shown that T C decreases with increasing cobalt content. In order to widen the field of investigation, especially the search for materials with possibility to be used in magnetic or electrical devices, we studied the properties of some manganites derived from the compound Pr 0.7 Sr 0.3 MnO 3 [ 29 ], whose lanthanide (or rare earth) is praseodymium, much less studied than its counterpart lanthanum.…”