3RD INTERNATIONAL CONGRESS ON TECHNOLOGY - ENGINEERING & SCIENCE - Kuala Lumpur - Malaysia (2017-02-09)

Structure And Magnetic Properties Of Fe-doped La2comno6 Compounds
Because of many interesting effects and spintronic applications, the perovskites attracted a lot of studies for long time. For the double perovskites A2BB’O6, the magnetic orders are decided strongly by order of B and B’ ions. La2CoMnO6 is material containing multi-magnetic phase transitions, low value of the magnetocaloric effect (MCE) but the colossal magnetoresistance (CMR), the giant dielectric constant also the large magnetodielectric effects[1,2,3]. With intention to adjust the magnetic orders, we substituted Co/Mn by Fe with different concentrations. The bulk samples of La2Co1-xFexMnO6 were prepared by solid state reaction method with concentrations of x = 0, 0.2, 0.4, 0.6, 0.8 and 1. The structure of samples at room temperature was checked by X-ray diffractometer using Cu-Kα radiation with step of diffraction angle 0.009o. The results pointed out that the samples are single phase and crystallized in a pseudo tetragonal structure, space group I4/mmm, No. 139 (Fig. 1), with different small changes of unit cell parameters along a- and c- axes, Table 1. The temperature and applied magnetic field dependences of magnetization were measured by a vibrating sample magnetometer (VSM) with T = 80-300 K and H = 0-10 kOe. The Fe doping led to decreasing of magnetization of samples. The Curie temperature for undoped-sample was about 210 K and reduced gradually for higher doping concentrations, Fig. 2(a). The magnetic entropy changes declined as an apparent consequence meaning that Fe doing is unprofitable for MCE application. The value of maximum magnetic entropy change (|Smax|) obtained under applied magnetic field change 10 kOe was 0.45 J.kg-1.K-1 for sample x = 0, Fig. 2(b). The analyses of isothermal magnetization M(H, T) data and the Arrott plots for case of x = 0 also showed a second order magnetic phase transition with a short-range ferromagnetic interaction order. The nature of these phenomena will be discussed thoroughly.
Duc Huyen Yen Pham, Dang Thanh Tran, T.V Manh, Wen-Zhe Nan, D.S Yang, S.C Yu