TY - JOUR

T1 - Lambda-peak in heat capacity II: solution to the problem

AU - Drebushchak, V. A.

N1 - The work was supported with the Russian Federation state assignment of the Sobolev Institute of Geology and Mineralogy SB RAS (State Registration Number: 122041400176-0).

PY - 2025/9/10

Y1 - 2025/9/10

N2 - In combining the hypothesis of molecular field by P. Weiss with the magnetization formula by W. Lenz, we obtained the model of the dipole system with two energy levels. The mathematical expression of the model is Δ = tanh((Δ + η)/τ), where Δ = f(η,τ) (0 < Δ < 1) is the function of two variables: reduced field η and reduced temperature τ. Two limiting cases of the model are the Schottky anomaly (for η → ∞) with the heat capacity ~ η dΔ/dτ and the magnetic phase transition at the Curie point (for η = 0) with derivative dΔ/dτ → ∞. Intermediate case for η ≪ 1 yields derivative dΔ/dτ reproducing the shape of heat capacity lambda-peak. Derivative dΔ/dτ is shown to approximate successfully the experimental CP data of ferromagnets in the vicinity of the Curie point with and without external magnetic field using only three fitting coefficients, for temperature, field, and proportionality between mathematical numbers and physical variables. The difference between experimental data and their approximation can be achieved below the experimental error.

AB - In combining the hypothesis of molecular field by P. Weiss with the magnetization formula by W. Lenz, we obtained the model of the dipole system with two energy levels. The mathematical expression of the model is Δ = tanh((Δ + η)/τ), where Δ = f(η,τ) (0 < Δ < 1) is the function of two variables: reduced field η and reduced temperature τ. Two limiting cases of the model are the Schottky anomaly (for η → ∞) with the heat capacity ~ η dΔ/dτ and the magnetic phase transition at the Curie point (for η = 0) with derivative dΔ/dτ → ∞. Intermediate case for η ≪ 1 yields derivative dΔ/dτ reproducing the shape of heat capacity lambda-peak. Derivative dΔ/dτ is shown to approximate successfully the experimental CP data of ferromagnets in the vicinity of the Curie point with and without external magnetic field using only three fitting coefficients, for temperature, field, and proportionality between mathematical numbers and physical variables. The difference between experimental data and their approximation can be achieved below the experimental error.

KW - Approximation

KW - Curie point

KW - Heat capacity

KW - Lambda-peak

KW - Magnetization

UR - https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=105015414967&origin=inward

UR - https://www.mendeley.com/catalogue/e0832185-07ea-34a5-8788-4c11618caacc/

U2 - 10.1007/s10973-025-14649-z

DO - 10.1007/s10973-025-14649-z

M3 - Article

JO - Journal of Thermal Analysis and Calorimetry

JF - Journal of Thermal Analysis and Calorimetry

SN - 1388-6150

ER -