Itinerant-Electron Weak Ferromagnetism in La-Based Filled Skutterudite LaFe₄As₁₂

Magnetic Properties of New Filled Skutterudite Compounds EuT4As12(T=Fe, Ru, and Os) Synthesized under High Pressure

“…In fact, several compounds exhibit exotic properties, including superconductivity in LnRu 4 As 12 (Ln ¼ La, Pr), 10) Kondo semiconducting behavior in CeT 4 As 12 (T ¼ Fe, Ru, and Os), [11][12][13] Kondo-lattice antiferromagnet PrOs 4 As 12 , 14,15) and itinerant-electron weak ferromagnetism in LaFe 4 As 12 . 16) However, only preliminary studies have been conducted on the properties of As-based compounds because the compounds are quite difficult to prepare. Recently, Henkie et al succeeded in growing single crystals of filled skutterudite arsenides with M ¼ La, Ce, Pr, and Th; T ¼ Fe, Ru, and Os by mineralization in a Cd:As flux in a custom-built highpressure cell filled with Ar (up to 40 atm).…”

Anomalous Behavior of Itinerant Weak Ferromagnet LaFe4As12in NMR/NQR Studies

“…These features are consistent with the theoretical prediction that the electronic density of states at Fermi level, N(E F ), monotonically increases with increasing of the lattice constant. [10][11][12] However, their ground states are different with one another; for X=P, it is reported that the electronic state changes from * E-mail address: 099s101s@stu.kobe-u.ac.jp † E-mail address:kotegawa@crystal.kobe-u.ac.jp ‡ E-mail address: tou@crystal.kobe-u.ac.jp an ordinary paramagnetic normal state to a conventional spinsinglet superconducting ground state at T c = 4.1 K. 11) On the other hand, LaFe 4 As 12 is reported to be a weakly itinerant ferromagnetic ground state due to Fe 3d electrons, 1) and LaFe 4 Sb 12 is an enhanced Pauli paramagnet close to a ferromagnetic (FM) quantum critical point exhibiting non-Fermi liquid (NFL) behaviors.13) It is still unclear what triggers their different ground states.In this paper, we report 75 As(I = 3/2)-NQR (nuclear quadrupole resonance) for LaFe 4 As 12 in order to investigate its electronic state from microscopic viewpoints. NMR studies have been already carried out in the high temperature region of 20 − 300 K by Nowak et al 1) In order to clarify the normal and ferromagnetic ground states more in detail , NMR/NQR measurements at low temperatures below 20 K are needed, so that we performed 75 As-NQR measurement in the temperature range of 2 − 250 K. Fig.…”

“…These features are consistent with the theoretical prediction that the electronic density of states at Fermi level, N(E F ), monotonically increases with increasing of the lattice constant. [10][11][12] However, their ground states are different with one another; for X=P, it is reported that the electronic state changes from * E-mail address: 099s101s@stu.kobe-u.ac.jp † E-mail address:kotegawa@crystal.kobe-u.ac.jp ‡ E-mail address: tou@crystal.kobe-u.ac.jp an ordinary paramagnetic normal state to a conventional spinsinglet superconducting ground state at T c = 4.1 K. 11) On the other hand, LaFe 4 As 12 is reported to be a weakly itinerant ferromagnetic ground state due to Fe 3d electrons, 1) and LaFe 4 Sb 12 is an enhanced Pauli paramagnet close to a ferromagnetic (FM) quantum critical point exhibiting non-Fermi liquid (NFL) behaviors.…”

“…Among filled skutterudite compounds, La-based filled skutterudites LaFe 4 X 12 (X=P, As, Sb) without f ion have been attracted much attention because of their anomalous magnetic properties. 10) In LaFe 4 X 12 , it is reported that the electronic state is a correlated itinerant electron system arising from Fe 3d electrons. In the paramagnetic state, when X is varied from P to As, and Sb, the electronic specific heat coefficient (γ s ) increases from 57, 78 and 200 mJ/(K 2 mol), respectively.…”

“…These features are consistent with the theoretical prediction that the electronic density of states at Fermi level, N(E F ), monotonically increases with increasing of the lattice constant. [10][11][12] However, their ground states are different with one another; for X=P, it is reported that the electronic state changes from an ordinary paramagnetic normal state to a conventional spinsinglet superconducting ground state at T c = 4.1 K.…”