Quenching and Recovery of Spin in Quasi-One-dimensional Itinerant Electron Magnet LaMn₄Al₈

Abstract

The electron correlation in the 3d heavy-electron compound with linear spin chains, LaMn 4 Al 8 , has been investigated. Like a similar compound, YMn 4 Al 8 , we found a broad maximum in the temperature dependence of the susceptibility. This is interpreted by assuming the presence of a narrow pseudogap with the width Á ' 280 K in the spin excitation spectrum, which leads to the quenching of spin at low temperatures. Anomalies in susceptibility, resistivity and thermal expansion data, observed below approximately 50 K in spite of the absence of any phase transition, suggest the recovery of spin and the development of short-range magnetic correlation in this low-temperature range. This is in contrast to the case of YMn 4 Al 8 . No apparent long-range ordering in spite of the markedly developed magnetic correlation is probably due to the one-dimensional nature of the Mn spin arrangement.

Negative magnetoresistivity of the RM4Al8 (R=Sc, Y, Ce, Yb, Lu; M=Cr, Mn, Fe) ternaries with the ThMn12-type crystal structure

“…According to the data of Refs. [25][26][27] the separation d c ≈ 2.7Å appears to be critical. At d < d c the Mn atoms do not have the local magnetic moment.…”

“…As it is known in the RMn 4 Al 8 long range magnetic ordering is absent [25][26][27]. In this case the magnetic state of the Mn sublattice is determined by the interatomic Mn-Mn separation, by the exchange interactions with the closest neighbors and by the temperature [25].…”

“…Now they can play a role of magnetic impurities and at the low temperature they can cause the Kondo effect. Recently, it has been shown that in the RMn 4 Al 8 compounds, in spite of the absence of the long range magnetic interactions the strongly developed spin fluctuations (SF) are present [25][26][27]. At low temperatures the fluctuations of the Mn moment become slower resulting supposedly in forming of the dynamical SG [26].…”

“…Recently, it has been shown that in the RMn 4 Al 8 compounds, in spite of the absence of the long range magnetic interactions the strongly developed spin fluctuations (SF) are present [25][26][27]. At low temperatures the fluctuations of the Mn moment become slower resulting supposedly in forming of the dynamical SG [26]. Thus the last phenomenon could be responsible for the damping of the Kondo effect and the decrease of the electrical resistivity with a diminution of the temperature observed by us in YMn 4 Al 8 .…”

NMR study on the low-temperature state of

“…A series of RMn 4 Al 8 (R ¼ La, Y, Lu and Sc) compounds with the tetragonal CeMn 4 Al 8 -type structure is one of unique itinerant electron systems with strong electron correlation [1][2][3][4]. Specific heat measurements for some of these compounds revealed large electronic specific heat coefficients and no phase transition [5].…”