Transport, magnetic and thermal properties of Pr doped LaSr₂Mn₂O₇: a Kondo-type behaviour of resistivity

Abstract

The interplay of spin, charge and lattice degrees of freedom in LaSr 2 Mn 2 O 7 (tetragonal, space group I 4/mmm) yields a variety of properties such as a CEtype charge ordering and an A-type spin ordering. We have studied the effect of partial replacement of La by Pr on the magnetic and thermal properties of this system. Compounds of the type La 1−x Pr x Sr 2 Mn 2 O 7 (0 x 1) have been prepared and are found to crystallize in the same tetragonal structure. Magnetization, electrical resistivity and specific heat measurements have been carried out on these compounds. Replacing La by Pr in this system affects both the electronic and the magnetic state of the system. It is observed that the charge ordering temperature and the net magnetic moment reduce with the incorporation of Pr in the lattice. In the antiferromagnetic state, the charge carriers in La 1−x Pr x Sr 2 Mn 2 O 7 behave like a weakly scattered two-dimensional gas whose resistivity (ρ) is a logarithmic function of temperature, T (ρ ∝ log T ), over a certain temperature interval. This behaviour is enhanced with increasing concentration of Pr in the samples and is proposed to originate from quantum interference. The electronic part of the specific heat shows the presence of the two transitions at T CO and T N and a contribution from antiferromagnetic magnons at low temperatures.

Low temperature thermopower and electrical transport in misfit Ca3Co4O9with elongatedc-axis

“…To measure resistivity a constant current was sent by a Keithley source mater (model 2400) and the corresponding voltage was recorded by a Keithley nanaovoltmeter (model 2182). The thermopower was measured using the seesaw method [17]. In this technique two identical heaters were mounted on the two ends of the sample.…”

Effect of copper on the magnetism of half doped bilayer manganite

“…Such a small ξ requires the presence of a strong disorder in the lattice which will produce bound rather than localized states for the carriers. (The density of states N 0 (E F ) required here was extracted from the heat capacity data of the parent compound [40] and is expected to remain essentially unchanged by the substitution of Mn by Cu). Resistivity usually contains a sizeable contribution from grain boundaries and may be the reason for the increase of Eρ as the grain size reduces with increasing copper concentration.…”