CaMn2Al10: Itinerant Mn magnetism on the verge of magnetic order

Abstract

We report the discovery of CaMn2Al10, a metal with strong magnetic anisotropy and moderate electronic correlations. Magnetization measurements find a Curie-Weiss moment of 0.83 µB/Mn, significantly reduced from the Hund's rule value, and the magnetic entropy obtained from specific heat measurements is correspondingly small, only ≈ 9 % of Rln 2. These results imply that the Mn magnetism is highly itinerant, a conclusion supported by density functional theory calculations that find strong Mn-Al hybridization. Consistent with the layered nature of the crystal structure, the magnetic susceptibility χ is anisotropic below 20 K, with a maximum ratio of χ [010] /χ [001] ≈ 3.5. A strong power-law divergence χ(T ) ∼ T −1.2 below 20 K implies incipient ferromagnetic order, and an Arrott plot analysis of the magnetization suggests a vanishingly low Curie temperature TC ∼ 0. Our experiments indicate that CaMn2Al10 is a rare example of a Mn-based weak itinerant magnet that is poised on the verge of ferromagnetic order.

The Case of Itinerant Magnetism in CaMn$_{2}$Al$_{10}$: Self-Consistent Renormalisation (SCR) Theory Study

“…Thus it should exhibit the phenomenon of localized magnetism. However, this is in contradiction to what is observed in the experiment [1], and in our current theoretical study. The reason is strong Mn-Al hybridisation and it is explained in section 4.…”

“…We have performed numerical calculations to obtain the static susceptibility by solving the equations (2.19), (2.24) and (2.25) self consistently and have compared it with the experimental data available [1]. The susceptibility obtained through SCR theory is in dimensionless form i.e.…”

“…Itinerant magnetism in Manganese(Mn) compounds is a rare phenomena. The reporting of a recent discovery of Mn-based weak itinerant magnetism in CaMn 2 Al 10 compound is therefore quite interesting [1]. In this compound Mn moments are very strongly hybridized with the conduction electrons and a much reduced moment results from correlations.…”

“…In metals, the Mn moments can be weakly hybridized, leading to the pronounced magnetic character of systems like MnX (X = P,As,Sb,Bi) [6,7,8], MnB [9], and RMn 2 X 2 (R = La,Lu,Y; X = Si,Ge) [10,11]. There is another class of metallic compounds like MnSi [1], YMn 2 [12], and HfMnGa 2 [13], in which the electronic fluctuations are so strong and there is no definite moment (or valence state). Therefore, the current need is to investigate such Mn-based magnetic compounds on theoretical grounds in order to check their ability towards potential applications [14].…”

Magnetism of a rhombohedral-type pyrochlore-derived Kagome series, Mn2R3Sb3O14(R = Rare-earths)

“…Thus, for instance, apart from well-known colossal magnetoresistance perovskite-based manganites [1], Mn pnictides LaMnPO [2], CaMn2As2 [3], and BaMn2As2 [4] which are insulators due to strong Coulomb interaction, and metals like binary Mn compounds [5], RMn2X2 (R= Rare-earths; X= Si, Ge) [6] exhibiting pronounced magnetic character due to Mn, reduced moment metallic systems like MnSi [7], YMn2 [8], HfMnGa2 [9], and most recently CaMn2Al10 on the verge of magnetic order [10], are of great interest. It is worthwhile to note that Mn tends to order magnetically at rather high temperatures, even in a family when other transition metals like Fe, Co, Ni and Cu do not exhibit magnetic moment, as demonstrated for RMn2X2 family [6].…”