The goal of this study is to obtain the information

The goal of this study is to obtain the information on the temperature Pepstatin A of the magnetic properties of the LSMO-0.07 and LSMO-0.125 compounds in the 4–240K temperature range, i.e., exactly where the unusual macroscopic properties of these materials are observed.
The experimental part The studies were carried out on a vibration magnetometer in the International Laboratory of High Magnetic Fields and Low Temperatures (Wroclaw, Poland). The weight of single-crystal samples was 121.95mg for LSMO-0.125 and 152.8mg for LSMO-0.07, respectively. The magnetic field was applied along the c axis; the measuring field was 0.2 T. The temperature dependences of the magnetization of the samples were obtained in the 4–240K temperature range.
Results and discussion Fig. 1a shows the temperature dependence of magnetization for the LSMO-0.07 sample under cooling. It is easy to notice that the curve changes its behavior in the vicinity of 130K, and this temperature, according to the phase diagram obtained in Ref. [5], corresponds to the PT from the high-temperature paramagnetic phase to the low-temperature non-collinear one, accompanied by the emergence of spontaneous and residual magnetization. This indicates that the magnetic structure is weakly ferromagnetic rather than purely antiferromagnetic [5]. In this case, let us represent the temperature dependence of magnetization М(Т) as the following power function: where ТС is the PT temperature, β is the critical exponent. It follows from the analysis of the data in Fig. 1a that this description (curve 2) is in sufficiently good agreement with the experimental curve. The following values were obtained for the parameters of function (1): TС=125.8(1.5) K, β=0.280(8). We also determined the PT temperature using the following procedure: the М(Т) dependence in the paramagnetic phase was approximated by a straight line to the region of low temperatures (curve 3 in Fig. 1a), and the intersection point with the approximating curve was found (see formula (1)). The obtained temperature value coincides with the above-listed value of ТС within ±0.5K. Fig. 1b shows the temperature dependence of magnetization M(T) for the LSMO-0.125 sample under cooling. It can be clearly seen that two anomalies are observed on the curve: the first one near 180K, and the second one near 157K; notice that the function М(Т) increases sharply below this temperature, and then practically does not change in the region below 100K. Thus, we can conclude that two magnetic phase transitions are observed in the LSMO-0.125 sample. In the 150–190K temperature range, the М(Т) dependence was also approximated by function (1) and the following parameters were obtained: ТС1=181.2(1.5) K and β1=0.440(13), which is sufficiently close to the value of the critical exponent equal to 0.5 for the mean field theory. The value of ТС1, obtained from the intersection point of line 3 (linear approximation of М(Т) of the paramagnetic phase to the low-temperature region) and curve 2 (power dependence of magnetization with the parameters ТС1 and β1), turned out to be similar to the case with the LSMO-0.07 sample, close (with greater accuracy than 0.5K) to the value of ТС1=181.2K, determined from formula (1). This temperature value is in good agreement with the result obtained in Ref. [5]. The second PT was approximated by a step function with ТС2 =157.6 (1.5) K. This transition apparently corresponds to the transition to the polaron or the polaro n-ordering phase [5,6]. Thus, based on the character of the temperature dependences of М(Т), and the values of the critical exponents obtained for the LSMO-0.07 and LSMO-0.125 samples, Hairpin can be assumed that the PT at 125.8K in the first sample and at 181.2K in the second one are the second order phase transitions, while the PT in the second sample (LSMO-0.125) at 157.6K is the first order phase transition. The final stage of our study involved constructing the temperature dependence of the reverse magnetization 1/M for both samples (Fig. 2); the slopes of these curves in the paramagnetic phase (high-temperature regions) were used to estimate the values of the magnetic moments of manganese ions in both samples.