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首页> 外文学位 >Tuning the electronic and magnetic phases in calcium barite, platinum antimonide and ytterbium platinum.
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Tuning the electronic and magnetic phases in calcium barite, platinum antimonide and ytterbium platinum.

机译：调整重晶石钙，锑化铂和and铂中的电子和磁性相。

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摘要

Enabled by the design and synthesis via flux growth of appropriate high quality single crystals, the origins of novel electronic and magnetic phenomena in systems that contain both itinerant carriers and local magnetic moments are sought.;The main subject of this thesis is the new quantum critical antiferromagnet, Yb3Pt4. Its phase diagram is unique among quantum critical materials. It is the only known example of an antiferromagnet (T N=2.4K) with a first order phase transition. Application of a magnetic field leads to a critical endpoint (CEP) at 1.2 K and 1.5 T and then to a quantum critical point (QCP) at 1.6 T as a second order phase line. Other known quantum critical antiferromagnets have entirely second order phase lines and no CEP.;It is remarkable that the transition to an antiferromagnetic state coincides with the formation of a Fermi liquid (FL). The FL crossover line does not terminate at the QCP as it does in other quantum critical materials, instead having a minimum near the CEP. The properties of the FL in Yb3Pt 4 are also unusual. It is surprising that the FL parameter, gamma (∝ m*) is largely field independent in the high field FL region. A diverging effective mass (m*) on approach to the QCP from the FL region is considered a hallmark of systems with a QCP. Measurements of the heat capacity, resistivity and magnetic susceptibility of Yb3Pt4 do not find this diverging m*, but instead find diverging magnetic interactions at zero field.;No non-Fermi liquid (NFL) behavior is observed in measurements of the heat capacity, magnetic susceptibility, or resistivity in Yb3Pt 4. This differs from the results for known quantum critical materials, which all show various types of NFL behavior extending over wide regions of temperature and magnetic field or pressure from the QCP.;Two other materials studied were CaB6, which displayed unexpected ferromagnetism in seemingly non-magnetic electron doped crystals, and rare earth doped PtSb2, which displayed potentially novel ferromagnetism and superconductivity, but in each case electron microprobe and acid etching experiments show that these phenomena originate with secondary impurity phases.
机译：通过适当的高质量单晶的通量生长的设计和合成，在包含流动载流子和局部磁矩的系统中寻找新颖的电子和磁性现象的起源。；本论文的主要主题是新的量子临界反铁磁体Yb3Pt4。其相图在量子关键材料中是唯一的。这是具有一阶相变的反铁磁体（TN = 2.4K）的唯一已知示例。施加磁场会导致在1.2 K和1.5 T下的临界端点（CEP），然后在1.6 T下产生二阶相线的量子临界点（QCP）。其他已知的量子临界反铁磁体完全具有二阶相线且没有CEP。值得注意的是，向反铁磁态的转变与费米液体（FL）的形成相吻合。 FL交叉线不像其他量子关键材料那样终止于QCP，而是在CEP附近具有最小值。 Yb3Pt 4中FL的性质也不常见。令人惊奇的是，FL参数γ（m *）在高场FL区域中在很大程度上与场无关。从FL区域进入QCP的有效质量（m *）发散被认为是具有QCP的系统的标志。 Yb3Pt4的热容，电阻率和磁化率的测量值未发现该发散的m *，而是在零磁场下发现了发散的磁相互作用。;在热容值，磁性的测量中未观察到非费米液体（NFL）行为Yb3Pt 4的磁化率或电阻率。这与已知的量子临界材料的结果不同，量子临界材料的所有结果都显示出各种类型的NFL行为在QCP的温度，磁场或压力的较宽范围内扩展。在看似非磁性的电子掺杂晶体中显示出意外的铁磁性，而在稀土掺杂的PtSb2中显示出潜在的新型铁磁性和超导性，但在每种情况下，电子微探针和酸蚀刻实验均表明这些现象源自次级杂质相。

著录项

  • 作者

    Bennett, Marcus C.;

  • 作者单位

    University of Michigan.;

  • 授予单位 University of Michigan.;
  • 学科 Physics Condensed Matter.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 157 p.
  • 总页数 157
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 O49;
  • 关键词

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