A study of magnetic, specific heat and resistivity properties in Ca 0.85 Eu 0.15 MnO 3 around the phase transition temperature Momin Hossain Khan a , Sudipta Pal a,n , Esa Bose b a Department of Physics, University of Kalyani, Kalyani, Nadia 741235, WB, India b Department of Engineering Physics, B. P. P. I. M.T., Kolkata 700052, WB, India article info Article history: Received 27 November 2013 Received in revised form 10 January 2014 Available online 18 January 2014 Keywords: Perovskite manganite Magnetic property Electrical property abstract Correlation between the magnetic, specific heat and resistivity properties around the phase transition temperature has been investigated in electron doped polycrystalline Ca 0.85 Eu 0.15 MnO 3 (CEMO) manga- nite. The magnetic data show the existence of the magnetic phase transition around T C ¼122 K under cooling from the paramagnetic (PM) to ferromagnetic (FM) state. The critical exponents determined from the Arrott plot are higher than the value expected from the Heisenberg model because of short range ferromagnetic ordering in the sample. The resistivity sharply rises at the magnetic phase transition temperature. Specific heat measurement exhibits a distinct peak near T C that can be interpreted in terms of the magnetic phase transition. & 2014 Elsevier B.V. All rights reserved. 1. Introduction Physical properties such as electrical resistivity, thermoelectric power, thermal conductivity, magnetization and specific heat have so far been studied extensively for the hole-doped manganites with predominating Mn 3 þ [1–4] whereas there are very few studies carried out on electron doped manganites with predominating Mn 4 þ ions [5–7]. Nevertheless, they are of considerable interest because the phase diagrams of hole and electron doped manganites are qualitatively different [8,9]. Most of the authors have reported on electron-doped polycrystalline CaMnO 3 manganites doped by Tb, Yb, Nd, Ho [10,11], Lu [12], La, Y, and Ce [13,14]. Some of the publications on electron-doped manganites were devoted to study- ing the magnetic and transport properties of polycrystalline Ca 1x Eu x MnO 3 (0 rx r0.3) [15,16], but these works have not been continued. Recently Naumov et al. studied Ca 0.85 Eu 0.15 MnO 3 single crystal and discussed their results with the properties of polycrys- talline sample [17]. The Ca 0.85 Eu 0.15 MnO 3 single crystal becomes a C type antiferromagnet with monoclinic crystal structure exhibiting charge/orbital ordering at 150 K. However Pnma crystal structure of polycrystalline Ca 0.85 Eu 0.15 MnO 3 shows the paramagnetic to ferro- magnetic phase transition [17]. Differences in the properties of single crystal and polycrystalline sample with the same content of Eu in CEMO are associated with the ordering of oxygen vacancies that appear during the crystal growth. Studies on magnetic property are significant in this system as the phase transition largely affects the electrical transport properties [18,19]. In this temperature dependent magnetic study, the critical exponents β, γ and δ provide important information concerning the interaction mechanisms near the paramagnetic-to-ferromagnetic (PM–FM) phase transition. These parameters also provide valuable information regarding the lattice dimension, dimension of order parameter and range of interaction. The phase transition in polycrystalline manganites can be correlated to the value of critical exponents to know whether they follow the mean-field theory (long range interaction) or the Heisenberg model (short range interaction) originates from mag- netic polaron. Further, the observed entropy change associated with the specific heat peak could provide information about the presence of magnetic inhomogeneties. In this paper, we report a systematic study of magnetization, specific heat, and electrical resistivity as a function of temperature in Ca 0.85 Eu 0.15 MnO 3 polycrystalline sample. 2. Experimental procedure The polycrystalline sample, CEMO was prepared by using a standard solid state reaction method. The precursors CaO, MnO 2 and Eu 2 O 3 (each of purity 99.9%) were mixed in proper stoichio- metric ratio, grounded and then preheated at 1170 K for 24 h. The mixed powder thus obtained was regrounded, pelletized in bar shape and sintered at 1520 K for 12 h. Finally the pellets were sintered at 1770 K for another 12 h and cooled systematically at the rate 21/min till 800 K and then furnace cooled to room temperature. Resistivity measurement was performed by standard four-probe method. The specific heat measurement was carried out by means of the relaxation method and the data were collected during the cooling process at room temperature under Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jmmm Journal of Magnetism and Magnetic Materials 0304-8853/$ - see front matter & 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jmmm.2014.01.013 n Corresponding author. Tel.: þ91 33 2582 2505; fax: þ91 33 2582 8282. E-mail address: sudipta.pal@rediffmail.com (S. Pal). Journal of Magnetism and Magnetic Materials 357 (2014) 24–28