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arXiv 1602.06360cond-mat.stat-mech
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具有竞争短程和长程相互作用的自旋3/2 Blume-Capel模型

The spin-3/2 Blume-Capel model with competing short- and long-range interactions

Octavio D. Rodriguez Salmon, Jose Ricardo de Sousa, Minos A. Neto, Igor T. Padilha, J. Roberto Viana Azevedo, Francisco Dinola Neto

摘要:

利用解析方法得到的自由能密度研究了具有短程和长程相互作用的自旋- $3/2$ Blume-Capel模型的相图.当强度为正的短程相互作用$K$排列成线性链时,会倾向于建立反平行的自旋序,而负的长程相互作用$-J$则倾向于使它们平行排列,竞争就出现了。因此,$K/J > 0.25$不存在铁磁有序。因此,通过改变该区间内的$K$值来扫描相图。与自旋为1的情况下所做的其他类似研究一样,当$K/J$大于某个临界值时,分离铁磁相和顺磁相的二级前沿逐渐转变为一级线。因此,有一个子区间$K$,其中两个三临界点出现限制二阶前沿的长度。然而,对于更大的值的$K/J$,铁磁-顺磁前线成为完全的一阶。此外,划分磁化强度$m=3/2$和$m=1/2$两个不同铁磁相的典型共存线通过产生另一条具有包围第三有序相的再入行为的共存线而变得更加复杂。在这种情况下,竞争使得在相图中存在一个区域,其中对于每个具有$S_{i}=3/2$的自旋$i$($S_{i}=-3/2$),存在另一个具有$S_{j}=-1/2$的自旋$j$($S_{j}=1/2$),因此每个自旋的磁化强度的绝对值为1。

英文摘要:

The phase diagrams of the spin-$3/2$ Blume-Capel model with competing short and long-range interactions were studied through the free energy density obtained by analytical methods. The competition emerges when positive short-range interactions of strength $K$ arranged in a linear chain tend to establish an anti-parallel spin order, whereas negative long-range interactions $-J$ tend to align them in parallel. Thus, no ferromagnetic order exists for $K/J > 0.25$. So, the phase-diagrams were scanned by varying the values of $K$ in this interval. As in other similar study done for the spin-1 case, the second-order frontier separating the ferromagnetic and the paramagnetic phases is transformed gradually into a first-order line, when $K/J$ is greater than a certain critical value. Accordingly, there is a subinterval of $K$, for which two tricritical points appear restricting the length of the second-order frontier. Nevertheless, for greater values of $K/J$, the ferromagnetic-paramagnetic frontier becomes wholly of first order. Also, the tipical coexistence line, which divides two different ferromagnetic phases of magnetization $m=3/2$ and $m=1/2$, becomes more complex by giving rise to another line of coexistence with a reentrant behavior that encloses a third ordered phase. In this case, the competition is such that there is a region in the phase diagram, where for each spin $i$ with $S_{i}=3/2$ ($S_{i}=-3/2$), there is another one spin $j$ with $S_{j}=-1/2$ ($S_{j}=1/2$), so the absolute value of the magnetization per spin is one.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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