The pseudogap and anisotropic thermal expansion in RMn₄Al₈(R = La,Y,Lu and Sc)

Abstract

The temperature dependence of the magnetic susceptibility shows a broad maximum at ∼550 and 630 K for LuMn(4)Al(8) and ScMn(4)Al(8), respectively, which can be interpreted as due to the presence of a pseudogap in the effective bands as in LaMn(4)Al(8) and YMn(4)Al(8). The anisotropic thermal expansion observed for RMn(4)Al(8) (R = La, Y, Lu and Sc) and the sensitive volume dependence of the gap width throughout the RMn(4)Al(8) system suggest dominant magnetic coupling in Mn spin chains along the c axis.

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].…”

Electronic structure and magnetic properties of RT4Al8 (R = Sc, Y, La, Lu; T = Fe, Mn, Cr) compounds. Hydrostatic pressure effects

“…The large spread in published data on the magnetic properties of RFe 4 Al 8 compounds is noteworthy and may be a consequence of the different techniques used to prepare the samples and of the high sensitivity of their characteristics to deviations from stoichiometry. More unique information on the magnetic properties has been obtained for RMe 4 Al 8 compounds with nonmagnetic elements R. 14,15 Magnetic ordering has not been observed in this system and the maxima in the v(T) curves observed at high temperatures (200-400 K) are apparently caused by the character of the band structure. 1063-777X/2016/42(6)/8/$32.00…”

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].…”