Physik-Department, Technische Universität München, James-Franck-Straße, D-85748 Garching, Germany.
Phys Rev Lett. 2013 Apr 26;110(17):177207. doi: 10.1103/PhysRevLett.110.177207.
We report high-precision measurements of the temperature and magnetic field dependence of the specific heat, C(T,H), across the magnetic phase diagram of MnSi. Clear anomalies establish the Skyrmion lattice unambiguously as a thermodynamic phase. The evolution of the specific heat anomalies, the field dependence of the entropy released at the phase transitions, and the temperature versus field dependence of crossover lines provide striking evidence of a tricritical point at μ0H(TCP)(int) = 340 mT and T(TCP) = 28.5 K. The existence of this tricritical point represents strong support of a helimagnetic Brazovskii transition, i.e., a fluctuation-induced first-order transition at H = 0.
我们报告了 MnSi 磁相图中比热 C(T,H)对温度和磁场的高精度测量。明显的异常明确地确立了斯格明子晶格作为热力学相。比热异常的演化、相变时释放的熵的场依赖性以及交叉线的温度与场依赖性，提供了在 μ0H(TCP)(int) = 340 mT 和 T(TCP) = 28.5 K 处存在三临界点的显著证据。这个三临界点的存在强烈支持了亚铁磁 Brazovskii 转变，即在 H = 0 时由涨落引起的一级相变。
