Investigaciones Investigaciones recientes en recientes en

nanoestructuras nanoestructuras magnéticasmagnéticas

José Luis Morán-LópezJosé Luis Morán-LópezFacultad de CienciasFacultad de Ciencias

Universidad Nacional Autónoma Universidad Nacional Autónoma de México, de México,

Red Temática de Nanociencias y Red Temática de Nanociencias y Nanotecnología, Querétaro, Qro.,Nanotecnología, Querétaro, Qro.,

Junio 2011Junio 2011

Dr. Alipio Calles MartínezDr. Alipio Calles Martínez Dr. Jorge Ramón SotoDr. Jorge Ramón Soto Dr. Bertha MolinaDr. Bertha Molina Dr. José Luis Morán LópezDr. José Luis Morán López

M.C. Raúl EspejelM.C. Raúl Espejel

Manganese NanostructuresManganese Nanostructures Manganese diamer and small clustersManganese diamer and small clusters Two dimensional Heusler AlloysTwo dimensional Heusler Alloys Endohedral manganese in gold Endohedral manganese in gold

nanostructuresnanostructures

Cobalt Nanowires with complex Cobalt Nanowires with complex structuresstructures

Chemical and magnetic order in Chemical and magnetic order in bimetallic nanoclustersbimetallic nanoclusters

Mn is a unique transition metal element with fascinating magnetic properties

• The description of Mn has been in general a difficult problem.

- The atomic electronic configuration is 3d5s2 with a µ=5µB

- The unfilled subshell lies 2.14 eV above the occupied and the atomic moment is resilient to minor changes.

- The atomic moment is conserved in doped semiconductors and couple ferromagnetically.

- Dilute solutions of Mn in Cu behave like a spin glass.

Is Mn2 van der Waals bonded with AF or FM coupling?

Magnetic Magnetic properties of properties of

small Mn small Mn clustersclustersJ. Mejía-López, A.H. Romero, M.E. García, and J. Mejía-López, A.H. Romero, M.E. García, and

J.L. Morán-LópezJ.L. Morán-López

Universidad Católica de ChileUniversidad Católica de Chile

Universidad de Kassel, AlemaniaUniversidad de Kassel, Alemania

CINVESTAV, Unidad QuerétaroCINVESTAV, Unidad Querétaro

Facultad de Ciencias, UNAMFacultad de Ciencias, UNAM

Experiment:Knickelbein, PRL 86, 5255 (2001)

Magnetic properties of small Mn-clusters

Phys. Rev. B 70, 014424 (2004)]

Manganeso Manganeso encapsulado en encapsulado en nanestructuras nanestructuras

de orode oroJorge Ramón Soto, Alipio Jorge Ramón Soto, Alipio Calles y Gerardo RaggiCalles y Gerardo Raggi

Se analizan las propiedades Se analizan las propiedades magnéticas de átomos de magnéticas de átomos de manganeso encapsulados con manganeso encapsulados con nanoestructuras de oro. nanoestructuras de oro.

Se estudian las estructuras de oro Se estudian las estructuras de oro limpio y pasivadas con tiolatos.limpio y pasivadas con tiolatos.

Two Dimensional Two Dimensional Heusler AlloysHeusler Alloys

R. Rodríguez-Alba, F. Aguilera-Granja and J.L. R. Rodríguez-Alba, F. Aguilera-Granja and J.L. Morán-LópezMorán-López

Instituto de Física, Universidad Autónoma de Instituto de Física, Universidad Autónoma de San Luis PotosíSan Luis Potosí

Facultad de Ciencias, Universidad Nacional Facultad de Ciencias, Universidad Nacional Autónoma de MéxicoAutónoma de México

Heusler alloys, are ternary systems X2MnZ that Heusler alloys, are ternary systems X2MnZ that have been know since 1903. These systems have have been know since 1903. These systems have Mn as one of the main components and show a Mn as one of the main components and show a rich variety of magnetic phases, depending on rich variety of magnetic phases, depending on the two other chemical components and on the the two other chemical components and on the temperature. temperature.

These alloys looked very promising for These alloys looked very promising for applications since Mn has a magnetic moment applications since Mn has a magnetic moment close to 4 µB. According to a previous close to 4 µB. According to a previous calculations the role of the X atoms is to calculations the role of the X atoms is to determine the lattice constant and the Z atoms determine the lattice constant and the Z atoms mediate the interactions between Mn atoms. mediate the interactions between Mn atoms.

Two dimensional Version

Magnetic Properties Magnetic Properties of Co Nanowires with of Co Nanowires with Complex GeometriesComplex Geometries

R. Guirado-López, J.M. Montejano-Carrizales R. Guirado-López, J.M. Montejano-Carrizales and J.L. Morán-Lópezand J.L. Morán-López

Instituto de Física, Universidad Autónoma de Instituto de Física, Universidad Autónoma de San Luis PotosíSan Luis Potosí

Facultad de Ciencias, Universidad Nacional Facultad de Ciencias, Universidad Nacional Autónoma de MéxicoAutónoma de México

Motivated by the technological interest Motivated by the technological interest involving the miniaturization of sensors involving the miniaturization of sensors and the continuous increase of the and the continuous increase of the magnetic storage density, techniques for magnetic storage density, techniques for fabrication and characterization have fabrication and characterization have been developed.been developed.

Molecular beam epitaxy or laser ablation Molecular beam epitaxy or laser ablation followed by nanolithography represent the followed by nanolithography represent the state of the art for producing state of the art for producing nanomagnets.nanomagnets.

Ordenamiento Químico y Ordenamiento Químico y Magnético en Magnético en

nanestructuras nanestructuras bimetálicasbimetálicas

Instituto de Física, Instituto de Física, Universidad Autónoma de Universidad Autónoma de

San Luis PotosíSan Luis PotosíFacultad de Ciencias, Facultad de Ciencias, Universidad Nacional Universidad Nacional Autónoma de MéxicoAutónoma de México

Elements that do not show magnetic phases in bulk Elements that do not show magnetic phases in bulk samples, like rhodium or palladium, display samples, like rhodium or palladium, display magnetic moments in small clusters. magnetic moments in small clusters.

The 4The 4dd transition metal macroscopic systems do transition metal macroscopic systems do not fulfill the Stoner criterion to develop not fulfill the Stoner criterion to develop permanent magnetic moments. permanent magnetic moments.

Since the reduction in dimensionality brings a Since the reduction in dimensionality brings a natural narrowing in the width of the electronic natural narrowing in the width of the electronic bands, it is expected that, at least in some elements bands, it is expected that, at least in some elements of that row, the electronic density of states at the of that row, the electronic density of states at the Fermi energy or its equivalent, increases to the Fermi energy or its equivalent, increases to the extent that the criterion is fulfilled.extent that the criterion is fulfilled.