Reorientation transition

In addition to the hexagonal-square transition, a reorientation transition of the hexagonal vortex lattice from a state with the diagonal of the rhombic unit cell along [110] direction to [100] direction has been observed for YNi2B2C (Paul et al. 1998). Figure 51b shows that for H applied perpendicular to c the transition to a (nearly) square lattice occurs at a field of about 1 Tesla and at 0.8 Tesla a reorientation transition of the diagonal of the rhombic cell takes place (Sakata et al. 2000). 

The symmetry changes of the vortex lattice in borocarbide superconductors affect their pinning properties as was shown for YNi2B2C (Silhanek et al. 2001). For the field orientation // c, the reorientation transition of the vortex lattice mentioned above was found to be associated with a significant kink in the volume pinning force Fp, whereas in the basal plane (for H c) the signature of nonlocal effects is a fourfold periodicity of Fp. 

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. 

Figure 3. The dependence of spin-reorientation transition temperature on the hydrogen pressure for Er2Fei4BHx.

The spin-reorientation transition in Er2Fei4B compound can be attributed to the competing of the uniaxial Fe sub lattice and the planar rare-earth sublattice anisotropy, with the former being dominant at higher temperatures and the latter being dominant at lower ones. 

A. Alavi, R. Lynden-Bell, and R. Brown (1999) Displacement and distortion of the ammonium ion in reorientational transition states of ammonium chloride and ammonium fluoride. J. Chem. Phys. 110, p. 5861... 

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