四硼化钬的场致磁态
Field Induced Magnetic States in Holmium Tetraboride
摘要：
用单晶中子衍射和磁化强度测量研究了受抑稀土四硼化物HoB $_4$的零场和场感生磁态。在零场，HoB $_4$显示磁相变在$T_{\mathrm{N1}}$ = 7.1 K的一个不相称的状态与传播矢量（$δ$，$δ$，$δ'$），其中$δ$ = 0.02和$δ'$ = 0.43和在$T_{\mathrm{N2}}$ = 5.7 K的一个非共线相称的反铁磁结构。零场极化中子衍射测量表明，尽管在5.7 K下有反铁磁有序，但无公度反射的强度虽然大大降低，但仍持续到1.5 K。在较低的温度下，沿$c$ -轴的磁场的应用程序最初重新建立的无公度相作为在一个狭窄的磁场范围内的主导磁状态，就在HoB $_4$订购与向上-向上-向下亚铁磁结构的特点是由$(h,k,\frac{1}{3})$ -型反射之间的18和24千奥斯特。该磁场范围由先前报道的$M/M_{\mathrm{sat}}$ = $\frac{1}{3}$磁化平台来标记，我们在磁化测量中也看到了这一点。21和33 kOe之间的区域的特征在于反铁磁反射强度的增加，例如（100），其最大值与$M/M_{\mathrm{sat}}\approx$ $\frac{3}{5}$的窄磁化平台的出现相一致。磁场的进一步增加导致33 kOe以上的偏振态的稳定，而在高达59 kOe的所有磁场中明显存在无公度反射。我们提出的$H-T$相图HoB $_4$的$H \parallel c$包含固定和过渡磁相重叠，并表现出显着的历史依赖性。
英文摘要：
A study of the zero field and field induced magnetic states of the frustrated rare earth tetraboride, HoB$_4$, has been carried out using single crystal neutron diffraction complemented by magnetisation measurements. In zero field, HoB$_4$ shows magnetic phase transitions at $T_{\mathrm{N1}}$ = 7.1 K to an incommensurate state with a propagation vector ($δ$, $δ$, $δ'$), where $δ$ = 0.02 and $δ'$ = 0.43 and at $T_{\mathrm{N2}}$ = 5.7 K to a non-collinear commensurate antiferromagnetic structure. Polarised neutron diffraction measurements in zero field have revealed that the incommensurate reflections, albeit much reduced in intensity, persist down to 1.5 K despite antiferromagnetic ordering at 5.7 K. At lower temperatures, application of a magnetic field along the $c$-axis initially re-establishes the incommensurate phase as the dominant magnetic state in a narrow field range, just prior to HoB$_4$ ordering with an up-up-down ferrimagnetic structure characterised by the $(h,k,\frac{1}{3})$-type reflections between 18 and 24 kOe. This field range is marked by the previously reported $M/M_{\mathrm{sat}}$= $\frac{1}{3}$ magnetisation plateau, which we also see in our magnetisation measurements. The region between 21 and 33 kOe is characterised by the increase in the intensity of the antiferromagnetic reflections, such as (100), the maximum of which coincides with the appearance of the narrow magnetisation plateau with $M/M_{\mathrm{sat}}\approx$ $\frac{3}{5}$. Further increase of the magnetic field results in the stabilisation of a polarised state above 33 kOe, while the incommensurate reflections are clearly present in all fields up to 59 kOe. We propose the $H-T$ phase diagram of HoB$_4$ for the $H \parallel c$ containing both stationary and transitionary magnetic phases which overlap and show significant history dependence.
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