| 1. |
- Amft, Martin, et al.
(författare)
-
First-principles calculations of optical and magneto-optical properties of Ga1-xMnxAs and MnAs
- 2009
-
Ingår i: Physica. B, Condensed matter. - : Elsevier BV. - 0921-4526 .- 1873-2135. ; 404:20, s. 3782-3788
-
Tidskriftsartikel (refereegranskat)abstract
- We present a first-principles density-functional investigation of the optical and magneto-optical properties of MnGa1-xAs (with x = 0,0.0625, and 1) systems. Our calculated dielectric function, magneto-optical Kerr effect, and magnetic circular dichroism spectra agree reasonably well with existing experimental results. A comparison of the optical and magneto-optical spectra of MnAs in the naturally occurring hexagonal phase and in the cubic zinc-blende structure is made. The differences in the spectral properties of these two phases could aid detection of MnAs in the zinc-blende structure. (C) 2009 Elsevier B.V. All rights reserved.
|
|
| 2. |
- Elgazzar, S, et al.
(författare)
-
Hidden order in URu2Si2 originates from Fermi surface gapping induced by dynamic symmetry breaking
- 2009
-
Ingår i: Nature Materials. - 1476-1122 .- 1476-4660. ; 8:4, s. 337-341
-
Tidskriftsartikel (refereegranskat)abstract
- Spontaneous, collective ordering of electronic degrees of freedom leads to second-order phase transitions that are characterized by an order parameter driving the transition. The notion of a 'hidden order' has recently been used for a variety of materials where a clear phase transition occurs without a known order parameter. The prototype example is the heavy-fermion compound URu2Si2, where a mysterious hidden-order transition occurs at 17.5 K. For more than twenty years this system has been studied theoretically and experimentally without a firm grasp of the underlying physics. Here, we provide a microscopic explanation of the hidden order using density-functional theory calculations. We identify the Fermi surface 'hot spots' where degeneracy induces a Fermi surface instability and quantify how symmetry breaking lifts the degeneracy, causing a surprisingly large Fermi surface gapping. As the mechanism for the hidden order, we deduce spontaneous symmetry breaking through a dynamic mode of antiferromagnetic moment excitations.
|
|
| 3. |
- Hild, K., et al.
(författare)
-
Magnetic Circular Dichroism in Two-Photon Photoemission
- 2009
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:5, s. 057207-
-
Tidskriftsartikel (refereegranskat)abstract
- We report the observation of magnetic circular dichroism (MCD) in two-photon photoemission (2PPE). The Heusler alloys Ni2MnGa and Co2FeSi were investigated by excitation with femtosecond laser light, showing MCD asymmetries of A = (3.5 +/- 0.5) x 10(-3) for Ni2MnGa and of A = (2.1 +/- 1.0) x 10(-3) for Co2FeSi, respectively. A theoretical explanation is provided based on local spin-density calculations for the magnetic dichroic response; the computed 2PPE MCD agrees well with the experiment. The observed 2PPE magnetic contrast represents an interesting alternative for future time-resolved photoemission studies on surface magnetism practicable in the laboratory.
|
|
