Low temperature magnetization of3He films
Low temperature magnetization of3He films
复制标题
3He薄膜的低温磁化
DOI：
10.1007/bf00753824
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发表时间：
1994
影响因子：
2
通讯作者：
H. Fukuyama
中科院分区：
文献类型：
--
作者：
P. Schiffer;M. O'Keefe;D. Osheroff;H. Fukuyama
我们用核磁共振方法研究了纯~3He在接枝油上的吸附情况。这样的薄膜被冷却到∼75μK，比以前的工作人员可以达到的温度低一个数量级。特别是，我们测量了固体第二原子层(M2)的磁化强度，它在低密度时表现出反铁磁(AFM)行为，在高密度时表现出铁磁(FM)行为。在AFM和FM密度下，我们可以在远低于交换能(J)的温度下测量M2。我们在原子力显微镜密度下的数据可能支持提出的那个阶段的模型。在Fm密度下，M_2(T=0)与第二层密度(P_2)成线性关系，M_2增加了1倍∼，ϱ_2增加了6%，表观J值增加了不到2倍，表明FM相与低密度相共存。我们的高温(T&gT；J)数据也支持这种两相模型。我们发现M2遵循二维海森堡铁磁体的预期行为，直到T≪J，这是对这种行为的第一次实验观察。我们也证实了k=0自旋波在决定这类系统的低温行为中的重要性。由于退磁效应，FM相中的核磁共振线形也发生了位移和展宽，支持两相共存模型。
We have made NMR studies of thin films of pure3He adsorbed on Graf oil. Such films were cooled to ∼ 75 μK, an order of magnitude colder than previous workers could attain. In particular, we measured the magnetization of the solid second atomic layer, (M2), which displays antiferromagnetic (AFM) behavior at low densities and ferromagnetic (FM) behavior at high densities. At both AFM and FM densities, we could measure M2at temperatures well below the exchange energy (J). Our data at the AFM densities may support a proposed model of that phase. At the FM densities, we have found that M2(T = 0) is linear in second layer density (p2) and rises by a factor of ∼7 with a 6% increase in ϱ2and less than a factor of 2 increase in the apparent value of J, suggesting that the FM phase coexists with a lower density AFM phase. Our high temperature (T >J) data also support such a two phase model. We find that M2follows the expected behavior for a 2 dimensional Heisenberg ferromagnet down to T ≪ J, the first experimental observation of such behavior. We also confirmed the importance of k = 0 spin waves in determining the low temperature behavior of such a system. The NMR lineshape in the FM phase also displayed shifts and broadening due to demagnetization effects which support the model of two phase coexistence.