Quantum phase transitions in NbFe 2 and Ca 3 Ru 2 O 7
Quantum phase transitions in NbFe 2 and Ca 3 Ru 2 O 7
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NbFe 2 和 Ca 3 Ru 2 O 7 中的量子相变
DOI：
10.1002/pssb.200983079
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
Duncan W
中科院分区：
文献类型：
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作者：
Duncan W
我们研究了两种过渡金属化合物的低温态：(i) nbfe2处于铁磁性的阈值上，在低温下通过稍微改变其组成可以被推入自旋排列态。据报道，nbfe2的化学计量学是d -金属体系中低温自旋密度波序的一个罕见例子。采用压力调谐、场调谐和成分调谐等方法研究了NbFe2的相图。在量子临界点附近，我们发现了明显的非费米液体形式的电阻率和热容，而在有序相深处，我们观察到强的、滞后的磁阻效应。（ii） ca3ru2o7在冷却时先发生磁转变（TN= 56 K），然后发生结构转变（TS= 48 K）。在低温下，大部分费米表面出现间隙，导致载流子密度很低，费米表面口袋很小。压力同时抑制tnand和tsand（约为3.5 GPa），诱导第三种低温状态，该状态至少可达7.5 GPa。
We examine the low temperature states of two transition metal compounds: (i) NbFe2is poised on the threshold of ferromagnetism and can be pushed into a spin‐aligned state at low temperature by modifying the composition slightly. Stoichiometric NbFe2has been reported as a rare example of low‐temperature spin density wave order in a d‐metal system. We have used pressure, field and composition tuning to examine the phase diagram of NbFe2. Near the quantum critical point, we find distinct non‐Fermi liquid forms of the resistivity and heat capacity, whereas we observe strong, hysteretic magnetoresistance effects deep in the ordered phase. (ii) Ca3Ru2O7undergoes first a magnetic transition (TN= 56 K) and then a structural transition (TS= 48 K) on cooling. Most of the Fermi surface is gapped out at low temperature, leading to a very low carrier density and small Fermi surface pockets. Pressure suppresses bothTNandTSand, forp> 3.5 GPa, induces a third low temperature state, which is robust up to at least 7.5 GPa.