Vol.:(0123456789) 1 3 Applied Physics A (2018) 124:668 https://doi.org/10.1007/s00339-018-2085-4 Infuence of the heat treatment on magnetization reversal of orthorhombic perovskites LaFe 0.5 Cr 0.5 O 3 P. V. Coutinho 1  · Petrucio Barrozo 1 Received: 18 November 2017 / Accepted: 31 August 2018 / Published online: 7 September 2018 © Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract In this work, we show the infuence of the thermal treatment on the reverse magnetization of the LaFe 0.5 Cr 0.5 O 3 compound. The bulk samples were prepared by the combustion method using urea as fuel. After combustion, the dry powder was thermally treated at 1000 °C and 1300 °C for 24 h. Structural properties of this samples were analyzed by X-ray difraction followed by Rietveld refnement. This study reveals that both samples are monophasic with orthorhombic structure (Pbnm). The magnetic properties were investigated by measurement of the magnetization as a function of temperature and magnetic feld carried out on a SQUID magnetometer MPMS-7T by Quantum Design. The measure of the magnetization as a func- tion of temperature with an external magnetic feld of 100 Oe reveals that the phenomenon of reverse magnetization (MR) is present only in sample thermally treated at 1300 °C. The hysteresis loop in 5 K shows a characteristic magnetic irrevers- ibility of compounds with weak ferromagnetic behavior. The weak ferromagnetism in this compound can be attributed to the canting of the antiferromagnetically ordered spins due to the presence of a Dzyaloshinskii–Moriya interaction. The sample thermally treated at 1300 °C shows a discrete increase of the magnetization in 7 T. 1 Introduction The magnetization reversal (MR) has been explored as an important tool to reach more efcient devices. The MR occurs when the resulting magnetic moment of the material is directed in the opposite direction to the external mag- netic feld, resulting in a negative magnetization in a spe- cifc range of temperature. Recently, unusual mechanisms to revert the magnetization such as applying an external electric feld [1, 2] has been observed. This phenomenon is very important to the developing of the spintronic and mag- netocaloric devices. However, the low temperature where this phenomenon occurs is a critical problem that needs to be solved before these materials can be efectively used to develop devices. The unusual MR induced by a change in the tem- perature was frst reported at 1953 by Gorter et al. [3] in LiFe 2.5−x Cr x O 4 compound. Kumar et al. [4] published a review paper with several materials where the MR induced by temperature is observed and discuss the possible mecha- nisms for the occurrence of this behavior in diferent com- pounds. The temperature where a spontaneous reversal magnetization occurs is denominated of compensation tem- perature (T comp ). Below T comp , there is a range of tempera- ture where the sign of the magnetization is inverted and the magnetic moment of the material has an opposite direction to external magnetic feld. The MR can be modifed and also destroyed by applying an external magnetic feld sufciently intense [5–7]. Among the materials with unusual MR, the orthochro- mites and orthoferrites with perovskite structure (ABO 3 ) have been highlighted mainly by shown a T comp close the room temperature [8]. The Néel temperature (T N ) in these compounds changes in accord with the element on A site with value between 623 and 738 K for the orthoferrites [9, 10] and between 112 and 282 K for orthochromites [10, 11]. In the frst reports about the MR in orthoferrites and orthochromites, this phenomenon was attributed to the mag- netic interactions between the ions placed at diferent sites (A site and B site) of the perovskite structure [8]. However, this efect is also observed in materials without a magnetic moment in A site. In these compounds, the MR has been attributed to the competition between diferent magnetic ions located on the B site of the perovskite. In this way, the * Petrucio Barrozo pbs@ufs.br 1 Departamento de Física, Universidade Federal de Sergipe, Rod. Marechal Rondon, s/n, São Cristóvão, SE 49100-00, Brazil