Transport and thermal properties of La 0.67Ca 0.33Mn 1− xM xO 3 (M=Fe, Zr and Hf)

• Published in: Journal of alloys and compounds Vol. 326; no. 1; pp. 65 - 68
• Main Authors: Sridharan, V., Seetha Lakshmi, L., Govindraj, R., Nithya, R., Natarajan, D.V., Radhakrishnan, T.S.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2001
• Subjects: Colossal magneto-resistive materials; Substitution; Transport properties; Transport properties; Substitution; Colossal magneto-resistive materials
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/S0925-8388(01)01233-6

Mn site substitution with Fe, Zr and Hf (≈1 at.%) were carried out in colossal magneto-resistive material La 0.67Ca 0.33MnO 3. It is found from the resistivity, ac susceptibility and specific heat ( C p) measurements that Zr and Hf substitutions suppress the transition temperature ( T c) more effectively than Fe substitution. The excess entropy under the C p curve associated with the magnetic transition also substantially lowered compared to that of undoped and Fe-doped systems. From the consideration of the excess entropy under the C p curve and the ionic radii, it is speculated that both Zr 4+ and Hf 4+ ions predominantly substitute Mn 3+ site. Larger suppression of T c is attributed to local strain produced due to larger ion substitution as well as hole filling due to replacement of trivalent ion (Mn 3+) with tetravalent ions (Hf 4+ and Zr 4+).