Ab initio prediction of magnetically dead layers in freestanding γ-Ce(111)

Abstract

It is well known that the surface of nonmagnetic α-Ce is magnetically ordered, i.e., γ-like. One then might conjecture, in agreement with previous theoretical predictions, that the γ-Ce may also exhibit at its surfaces even more strongly enhanced γ-like magnetic ordering. Nonetheless, our result shows that the (111)-surfaces of magnetic γ-Ce are neither spin nor orbitally polarized, i.e., α-like. Therefore, we predict, in contrast to the nonmagnetic α-phase which tends to produce magnetically ordered γ-like thin layers at its free surfaces, the magnetic γ-phase has a tendency to form α-like dead layers. This study, which explains the suppressed (promoted) surface magnetic moments of γ-Ce (α-Ce), shows that how nanoscale can reverse physical properties by going from bulk to the surface in isostructural α-and γ-phases of cerium. We predict using our freestanding surface results that a typical unreactive and non-diffusive substrate can dramatically influence the magnetic surface of cerium thin films in contrast to most of the uncorrelated thin films and strongly correlated transition metals. Our result implies that magnetic surface moments of α-Ce(111) can be suddenly disappeared by increasing lattice mismatch at the interface of a typical unreactive and non-diffusive substrate with cerium overlayers.

Theoretical study of α-U/W(110) thin films from density functional theory calculations: Structural, magnetic and electronic properties

“…Hence, the structure of uranium can cause to reverse the magnetic properties from its bulk to its surfaces and inversely from its surfaces to its bulk. Similar results were recently reported 14 for the isostructural αand γ-Ce systems.…”

“…Stojić and coworkers employing the FP-augmented plane waves (FP-APW) method have shown that the α-U compound is a nonmagnetic system in its bulk form, whereas it behaves as a magnetic system with the imposed spin MM of 0.84µ B at its freestanding surfaces 11 . A typical substrate can affect the structure 13 and magnetism 14 of the overlayers that can give rise to a variety of lattice mismatches and as a result to various U-U interlayer (IL) spacings (ILSs). The U-U spacing can change the degree of 5f localizations and thereby electronic structures.…”

Pressure dependency of localization degree in heavy fermion CeIn3: A density functional theory analysis

“…Dependence of the lattice parameter to the correlations among 4f-electrons is in agreement with the previous results for the isostructural α - and γ -Ce compounds. The GGA + U with U eff = 4.4 eV (PBE-GGA) predicts 35 the larger (smaller) lattice parameter of the fcc γ -Ce ( α -Ce) in agreement with experiment. The B3LYP with α = 0.2 lattice parameter is larger and bulk modulus is smaller than those of GGA + U.…”

Mechanical properties and variation in SOC going from La to Nd in intermetallic RIn3 and RSn3 (R = La, Ce, Pr, Nd)

“…31 The exchangecorrelation effects are calculated within the local density approximation (LDA), 32 generalized gradient approximation (GGA), 33 GGAsol, 34 Wu-Cohen GGA (WC-GGA), 35 meta GGA (m-GGA) 36 and hybrid functional B3PW91 37,38 with spin polarization. As lanthanides are strongly correlated systems with localized 4f electrons, 39,40 to obtain the exact nature of the electronic structure of the compounds under consideration, we used LDA + U and GGA + U methods. The DFT + U method is based on the Hubbard model, which treats the strongly correlated electron systems with an orbital dependent potential of Coulomb and exchange interactions.…”