Magnon contribution to the specific heat and the validity of power laws in antiferromagnetic crystals

Magnetic Structure and Properties of the Na2CoP2O7 Pyrophosphate Cathode for Sodium-Ion Batteries: A Supersuperexchange-Driven Non-Collinear Antiferromagnet

“…Finally, the magnetic entropy was calculated as S mag = ∫ 0 T C p,mag /T dT with C p,mag extrapolated between the lowest measured temperature (2 K) and 0 K as C p,mag αT 3 , assuming a spin-wave model for a 3D antiferromagnet. 28 The total magnetic entropy saturates at a value of 10 J mol −1 K −1 , which is consistent with the theoretical value S mag = R ln(2S + 1) = 11.5 J mol −1 K −1 for Co 2+ in the S = 3 / 2 spin state. Note that only approximately one-third of the total entropy is gained at T N , which also suggests that the λ-type anomaly at 6.5 K is associated with 3D ordering, whereas at higher temperature, the magnetic entropy is associated with short-range two-dimensional (2D) correlations.…”

“…Finally, the magnetic entropy was calculated as S mag = ∫ 0 T C p ,mag / T d T with C p ,mag extrapolated between the lowest measured temperature (2 K) and 0 K as C p ,mag α T 3 , assuming a spin-wave model for a 3D antiferromagnet . The total magnetic entropy saturates at a value of 10 J mol –1 K –1 , which is consistent with the theoretical value S mag = R ln(2 S + 1) = 11.5 J mol –1 K –1 for Co 2+ in the S = 3 / 2 spin state.…”

Anomalous Eu Valence State and Superconductivity in Undoped Eu3Bi2S4F4

“…The low-temperature C ( T ) data ( T < 2 K) are predominately from magnetic contributions, which can be fitted by the sum of a linear term and a quadratic term. The quadratic term can be ascribed to the excitations of 2D antiferromagnetic spin waves . The linear term, which generally appears in a spin glass state, implies existence of spin glass that probably occurs in the Eu(2) sublattice due to the Eu mixed valence.…”

Anomalous Eu Valence State and Superconductivity in Undoped Eu3Bi2S4F4

“…The quadratic term can be ascribed to the excitations of 2D antiferromagnetic spin waves. 47 The linear term, which generally appears in a spin-glass state, 48 implies existence of spin glass that probably occurs in the Eu(2) sublattice due to the Eu mixed valence. The large magnetic signal of ∼ 20 J K −1 mol −1 prevents the direct observation of a possible jump in C(T ), estimated to be ∼ 0.2 J K −1 mol −1 , associated with the superconducting transition around 1.5 K. Nevertheless, we indeed observed a kink at 1.43 K (see the lower right inset of Figure 5a) that could be related to the superconducting transition, when subtracting the contributions from magnetism (the linear and quadratic terms), electrons and lattice.…”