Magnetic spin reorientation

Figure 8.5 (a) Zeeman-shifted energy levels, (b) Cross section for magnetic spin reorientation. 

Scientific awareness of a low-temperature transition in magnetite began in 1929 with the observation of a A-type anomaly in the specific heat at about 120 K. The anomaly was typical of an order-disorder transition, but it was well below the magnetic-ordering temperature Tc = 850 In 1931, Okamura observed an abrupt semiconductor-semiconductor transition near 120 K. The transition exhibits no thermal hysteresis, but the transition temperature is sensitive to the oxygen stoichiometry. More recent specific-heat measurements show the presence of two resolvable specific-heat peaks at the transition temperature the lower-temperature peak near 110 K appears to be due to a spin reorientation. 

Fig. 34. Temperature dependence of the hyperfine field components along the tetragonal b and c axes, (W, r)b and (Whf)c, of a GdNi2B2C sample, reflecting the temperature dependence of the corresponding components of the Gd magnetic moment. The lines leading to the ordering temperature Tn = 20 K and the spin reorientation temperature Tr = 14 K are guides for the eye (after Tomala et al. 1998).

Ivanova, T.I., Pastushenkov, Yu.G., Skokov, K.P., Telegina, I.V., Tskhadadze, I.A. (1998) Spin-reorientation transitions and magnetic anisotropy in TbFen-xCoxTi compounds, J.Alloys Comp. 280 20-25. 

The intrinsic magnetic properties of the Er2Fei4B intermetallic compound have been previously investigated [1], According to the literature data [1,2] the magnetic ordering temperature of this compound is Tc = 554 K. Er2Fei4B exhibits one successive spin reorientation transition (SRT) at about 325 - 327 K. 

The aim of this work is to study the effect of hydrogenation on the magnetic phase transitions (Curie and spin-reorientation transition temperatures) in the Er2Fei4B compound using the magnetization measurements with continuous control of the hydrogen content in the examined sample. 

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