Low Temperature Heat Capacity of polycrystalline MnSi

Abstract

The itinerant helimagnet MnSi has been investigated by heat capacity using relaxation calorimetry in H=0. The paramagnetic to helimagnetic transition temperature Tc is found to be 29.6 K. Low temperature heat capacity data in the range 2-18 K is fitted with a usual electronic and phonon contribution. However, an additional magnetic term T ^3/2 needs to be added to witness the role of spin wave excitations in the magnetically ordered state below T_c. As well the energy gap on the order A=1.29 meV in the spin wave spectrum is evidenced. Small value of magnetic coefficient δ = 1.66 mJmol^-1K^-5/2 hints the itinerant nature of the magnetism in MnSi. Obtained coefficients gives the Debye temperature θ_D = 534 K and the Sommerfeld coefficient of specific heat γ = 0.0367 Jmol^-1K^-2. Noteworthy observation is the negative trend in the magnetic part of the entropy after T_c.