Direct calorimetric measurements of isothermal entropy change on single   crystal W-type hexaferrites at the spin reorientation transition
  We report on the magnetic field induced isothermal entropy change, \Delta s(Ha, T), of W-type ferrite with CoZn substitution. Entropy measurements are performed by direct calorimetry. Single crystals of the composition BaCo$_0.62$Zn$_1.38$Fe$_16$O$_27$, prepared by the flux method, are measured at different fixed temperatures under an applied field perpendicular and parallel to the c axis. At 296 K one deduces a value of K$_1$ = 8.7 \times 10^{4} J m$^-3$ for the first anisotropy constant, which is in good agreement with the literature. The spin reorientation transition temperature is estimated to take place between 200 and 220 K. 
Martino Lobue (SATIE, IA), Vincent Loyau (SATIE), Fr\'ed\'eric   Mazaleyrat (SATIE), Alexander Pasko (SATIE), Vittorio Basso...
cond-mat.mtrl-sci