论文标题
改良的立方尖晶石化合物lini $ _ {0.5} $ mn $ _ {1.5} $ o $ $ $ _ {4}
Unconventional superparamagnetic behavior in the modified cubic spinel compound LiNi$_{0.5}$Mn$_{1.5}$O$_{4}$
论文作者
论文摘要
经过修改的立方尖晶石化合物lini $ _ {0.5} $ Mn $ _ {1.5} $ o $ $ $ _ {4} $的结构，电子和磁性是通过X射线衍射，电阻率，DC和AC磁化，热量和热量容量，中子衍射，$^7 $ ucutain Encormation Remonnance效应，磁性磁性效应和磁性效应，通过X射线衍射，DC和AC磁磁来研究。我们将这种化合物稳定在具有空间群$ p4_ {3} 32 $的立方结构中。它具有$Δ/k _ {\ rm b} \ simeq 0.4 $ eV的电子带隙的半导体字符。每个Mn $^{4+} $和Ni $^{2+} $ sub-lattice以及Mn $^{4+} $和Ni $^{2+} $ sublattices之间的相互作用被发现是Ferromagnetic（FM）和抗Ferromagnetic的$ the $ the to to to to to to to to to to t to to to t to to to a ferm。 C} \ Simeq 125 $ 〜k。挫折参数（$ f $）和有序矩的降低值反映了由于FM和AFM相互作用而引起的磁性挫败感。从$^7 $ li nmr shift vs易感图中，平均超精细耦合在$^7 $ li nuclei和Ni $^{2+} $和Mn $^{4+} $之间，计算为$ \ sim 672.4 $ 〜oe/$ 〜oe/$μ__ {\ rm b} $。使用修改后的artott图，kouvel-fisher图和磁化等温度的通用缩放率，在$ t _ {\ rm c} $附近完成了详细的关键行为研究。估计的关键指数对应于3D XY通用类别。观察到大磁含量效应，熵的最大等温变化$ΔS_M\ simeq-11.3 $ 〜J/kg-k和最大的相对冷却能力$ rcp \ simeq 604 $ 〜j/kg，用于9〜t磁场的变化。 AC敏感性的虚构部分描绘了$ t = t _ {\ rm f2} $远低于阻止温度$ t _ {\ rm b} \ simeq120 $ 〜k的强频率依赖的驼峰。频率依赖性$ t _ {\ rm f2} $的ARRHENIUS行为和ZFC存储器的缺失证实了在铁磁有序状态中存在超级Paramagnetism。
Structural, electronic, and magnetic properties of modified cubic spinel compound LiNi$_{0.5}$Mn$_{1.5}$O$_{4}$ are studied via x-ray diffraction, resistivity, DC and AC magnetization, heat capacity, neutron diffraction, $^7$Li nuclear magnetic resonance, magnetocaloric effect, magnetic relaxation, and magnetic memory effect experiments. We stabilized this compound in a cubic structure with space group $P4_{3}32$. It exhibits semiconducting character with an electronic band gap of $Δ/k_{\rm B} \simeq 0.4$ eV. The interaction within each Mn$^{4+}$ and Ni$^{2+}$ sub-lattice and between Mn$^{4+}$ and Ni$^{2+}$ sublattices is found to be ferromagnetic (FM) and antiferromagnetic (AFM), respectively which leads to the onset of a ferrimagnetic transition at $T_{\rm C} \simeq 125$~K. The reduced values of frustration parameter ($f$) and ordered moments reflect magnetic frustration due to competing FM and AFM interactions. From the $^7$Li NMR shift vs susceptibility plot, the average hyperfine coupling between $^7$Li nuclei and Ni$^{2+}$ and Mn$^{4+}$ spins is calculated to be $\sim 672.4$~Oe/$μ_{\rm B}$. A detailed critical behaviour study is done in the vicinity of $T_{\rm C}$ using modified-Arrott plot, Kouvel-Fisher plot, and universal scaling of magnetization isotherms. The estimated critical exponents correspond to the 3D XY universality class. A large magneto-caloric effect is observed with a maximum isothermal change in entropy $ΔS_m \simeq - 11.3$~J/Kg-K and a maximum relative cooling power $RCP \simeq 604$~J/Kg for 9~T magnetic field change. The imaginary part of the AC susceptibility depicts a strong frequency dependent hump at $T=T_{\rm f2}$ well below the blocking temperature $T_{\rm b}\simeq120$~K. The Arrhenius behaviour of frequency dependent $T_{\rm f2}$ and the absence of ZFC memory confirm the existence of superparamagnetism in the ferrimagnetically ordered state.
