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|Type:||Artigo de periódico|
|Title:||Magnetoresistivity as a probe to the field-induced change of magnetic entropy in RAl2 compounds (R=Pr,Nd,Tb,Dy,Ho,Er)|
|Abstract:||The heat capacity C-P(T) of the ferromagnetic compounds RAl2 (R=Pr,Nd,Tb,Dy,Ho,Er) was measured at zero and applied magnetic field of 5 T in the temperature interval from 2 to 200 K. From these results are calculated the magnetic component of the entropy change, -Delta S-mag(T)=S(0,T)-S(H,T). From resistivity measurements, rho(H,T), from 2 to 300 K in the same compounds, we calculated the resistivity change due to the applied magnetic field, -Delta rho(mag)(T)=[rho(mag)(0,T)-rho(mag)(H,T)]. The results are compared and we observed a similar dependence between -Delta rho(mag)(T) and (T/T-C)(m)Delta S-mag(T) with m=0 for T >= T-C and m=1 for T <= T-C. A simple model using a Hamiltonian considering molecular and crystalline electric fields, in a mean field approximation, is adopted for the calculus. Our results show that theory and experiment are in good agreement showing that the magnetoresistivity is a probe to the field-induced change of magnetic entropy in these compounds and can be extended to other materials. A model for the factor connecting both quantities, -Delta S-mag(T) and -Delta rho(mag)(T), is developed. This factor contains mainly the effective exchange integral which is related to Fermi energy that in turn is related to the electron effective mass.|
|Editor:||American Physical Soc|
|Appears in Collections:||Artigos e Materiais de Revistas Científicas - Unicamp|
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