Lattice-parameter dependence of ferromagnetism in bcc and fcc iron

Bagayoko, Diola; Callaway, Joseph

doi:10.1103/physrevb.28.5419

Cited by 197 publications

(55 citation statements)

References 18 publications

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“…However, upon direct ion irradiation a decrease in the saturation magnetization of the near-surface region has been observed [6] which eventually renders the surface nonmagnetic [7][8][9][10]. This effect is coupled with an increasing coercivity with dose that is attributed to several phenomena including ion-induced damage of the crystal structure, the introduction of scattering defects within the thin-film and the emergence of lattice stress from the inclusion of the large impurity ions [11,12]. These previous works have tended to focus on the high dose regime where damaging effects of the ion irradiation can be observed clearly.…”

Section: Introductionmentioning

confidence: 99%

Focused-ion-beam induced interfacial intermixing of magnetic bilayers for nanoscale control of magnetic properties

Burn

Hase

Atkinson

2014

J. Phys.: Condens. Matter

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Modification of the magnetic properties in a thin-film ferromagnetic/non-magnetic bilayer system by low-dose focused ion-beam (FIB) induced intermixing is demonstrated. The highly localized capability of FIB may be used to locally control magnetic behaviour at the nanoscale. The magnetic, electronic and structural properties of NiFe/Au bilayers were investigated as a function of the interfacial structure that was actively modified using focused Ga + ion irradiation. Experimental work used MOKE, SQUID, XMCD as well as magnetoresistance measurements to determine the magnetic behavior and grazing incidence x-ray reflectivity to elucidate the interfacial structure. Interfacial intermixing, induced by low-dose irradiation, is shown to lead to complex changes in the magnetic behavior that are associated with monotonic structural evolution of the interface. This behavior may be explained by changes in the local atomic environment within the interface region resulting in a combination of processes including the loss of moment on Ni and Fe, an induced moment on Au and modifications to the spin-orbit coupling between Au and NiFe.

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Section: Introductionmentioning

confidence: 99%

Focused-ion-beam induced interfacial intermixing of magnetic bilayers for nanoscale control of magnetic properties

Burn

Hase

Atkinson

2014

J. Phys.: Condens. Matter

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“…However, as with magnetic bcc Fe, the spin densities give rise to distinct topologies. In the case of fcc (γ) Fe, three magnetic phases are observed, high-spin, lowspin, and paramagnetic (HS, LS, and PM respectively) phases, each characterized by a different range of lattice constants [27][28][29][30][31][32]. From the VASP calculations we find the HS phase corresponds to a ≥ 3.564Å, while the LS, low volume phase, occurs for a ≤ 3.563Å, with the PM phases equilibrating at a = 3.45Å.…”

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confidence: 99%

Topology of the Spin-Polarized Charge Density in bcc and fcc Iron

2008

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We investigate the topology of the spin-polarized charge density in bcc and fcc iron. While the total spin-density is found to possess the topology of the non-magnetic prototypical structures, in some cases the spin-polarized densities are characterized by unique topologies; for example, the spin-polarized charge densities of bcc and high-spin fcc iron are atypical of any known for nonmagnetic materials. In these cases, the two spin-densities are correlated: the spin-minority electrons have directional bond paths with deep minima in the minority density, while the spin-majority electrons fill these holes, reducing bond directionality. The presence of two distinct spin topologies suggests that a well-known magnetic phase transition in iron can be fruitfully reexamined in light of these topological changes. We show that the two phase changes seen in fcc iron (paramagnetic to low-spin and low-spin to high-spin) are different. The former follows the Landau symmetrybreaking paradigm and proceeds without a topological transformation, while the latter also involves a topological catastrophe. Bader's topological theory of molecular structure, Atoms in Molecules (AIM), has been successfully applied to a variety of crystalline systems [1][2][3][4][5][6][7][8][9][10][11]. It has been employed to investigate the nature of bonding in materials ranging from high temperature alloys to biological systems. These have yielded surprising results, such as second neighbor bond paths in B2 ionic crystals [3] and transition metal aluminides [4], with the magnitude of the latter correlating to failure properties [5]. Other studies have used bond path properties to offer first principles explanations of stress-induced failure in brittle and ductile alloys [7], as well as shear elastic constants in a variety of pure metals and alloys [8][9][10]. Building on these ideas and using the rigorous definitions of bond paths afforded by the theory, the anomalous behavior of iridium under shear was also explained [11].One of the attractive features of AIM is its reliance on the charge density, a quantum mechanical observable, that is most often calculated but can, in principle, be measured via X-ray diffraction techniques [12][13][14][15]. In a similar fashion, the spin-polarized charge density is an observable that can be calculated or measured using spinpolarized neutron diffraction. Despite the information and insights that have come from topological investigations of the total charge density, the same analysis has yet to be performed on spin-polarized densities. Here, we report the results from the first such studies, exploring the spin-minority and spin-majority topologies of bodycentered-cubic (bcc) and face-centered-cubic (fcc) iron.This first application of AIM to spin-density sheds light on the origins of the magnetic phase transitions of fcc iron. It is argued that this system undergoes two distinct phase transitions during volume expansion: a second- * Electronic address: trjones@mines.edu order phase change, from a paramagnetic to a l...

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“…The similar rapid change of the magnetic moment was observed for pure fcc iron for the radius of the Wigner-Seitz sphere equal to about 2.7 a.u. [6]. That reduction of the magnetic moment is connected mainly with changes of the density of majority states Fe(A,C) near the Fermi energy.…”

Section: Resultsmentioning

confidence: 98%

“…It is well known that magnetic moment of pure iron depends strongly on a value of the Wigner-Seitz radius [6]. Thus we suspect that also in Fe 3−x Cr x Al alloys volume effect is of great importance while considering magnetic properties.…”

Section: Introductionmentioning

confidence: 99%