论文标题
磁性渗透过渡附近的相边界
Phase boundary near a magnetic percolation transition
论文作者
论文摘要
由最近的实验观察激励[物理学。 Rev. 96，020407（2017）]在六角形铁氧体上，我们重新审视靠近晶格渗透阈值的稀释磁体的相图。我们在简单的立方晶格和代表六边形铁氧体的晶体结构上，对XY和海森堡模型进行了大规模的蒙特卡洛模拟。接近渗透阈值$ p_c $，我们发现磁性顺序温度$ t_c $取决于稀释$ p $通过电源法$ t_c \ sim | p_c | p-p_c |^ϕ $带有指数$ ϕ = 1.09 $，与经典的渗透理论一致。但是，这个渐近关键区域非常狭窄，$ | p-p_c | \ Lessim 0.04 $。在其之外，在广泛的稀释液中，通过非单亲权力定律很好地描述了相边界的形状，其指数略低于统一。尽管如此，渗透方案并未重现PBFE $ _ {12 -x} $ _ {12 -x} $ _x $ ga $ _x $ o $ o $ $ o $ $ $ o $ $ o $ o $ $ _ {19} $的实验观察到的关系$ t_c \ sim（x_c -x）^{2/3} $。我们讨论了我们发现的普遍性，以及对稀释的六边形铁氧体物理学的影响。
Motivated by recent experimental observations [Phys. Rev. 96, 020407 (2017)] on hexagonal ferrites, we revisit the phase diagrams of diluted magnets close to the lattice percolation threshold. We perform large-scale Monte Carlo simulations of XY and Heisenberg models on both simple cubic lattices and lattices representing the crystal structure of the hexagonal ferrites. Close to the percolation threshold $p_c$, we find that the magnetic ordering temperature $T_c$ depends on the dilution $p$ via the power law $T_c \sim |p-p_c|^ϕ$ with exponent $ϕ=1.09$, in agreement with classical percolation theory. However, this asymptotic critical region is very narrow, $|p-p_c| \lesssim 0.04$. Outside of it, the shape of the phase boundary is well described, over a wide range of dilutions, by a nonuniversal power law with an exponent somewhat below unity. Nonetheless, the percolation scenario does not reproduce the experimentally observed relation $T_c \sim (x_c -x)^{2/3}$ in PbFe$_{12-x}$Ga$_x$O$_{19}$. We discuss the generality of our findings as well as implications for the physics of diluted hexagonal ferrites.
