126 research outputs found
Cooling and heating by adiabatic magnetization in the NiMnIn magnetic shape memory alloy
We report on measurements of the adiabatic temperature change in the inverse
magnetocaloric NiMnIn alloy. It is shown that this alloy
heats up with the application of a magnetic field around the Curie point due to
the conventional magnetocaloric effect. In contrast, the inverse magnetocaloric
effect associated with the martensitic transition results in the unusual
decrease of temperature by adiabatic magnetization. We also provide
magnetization and specific heat data which enable to compare the measured
temperature changes to the values indirectly computed from thermodynamic
relationships. Good agreement is obtained for the conventional effect at the
second-order paramagnetic-ferromagnetic phase transition. However, at the first
order structural transition the measured values at high fields are lower than
the computed ones. Irreversible thermodynamics arguments are given to show that
such a discrepancy is due to the irreversibility of the first-order martensitic
transition.Comment: 5 pages, 4 figures. Accepted for publication in the Physical Review
Effect of Co and Fe on the inverse magnetocaloric properties of Ni-Mn-Sn
At certain compositions Ni-Mn- Heusler alloys (: group IIIA-VA
elements) undergo martensitic transformations, and many of them exhibit inverse
magnetocaloric effects. In alloys where is Sn, the isothermal entropy
change is largest among the Heusler alloys, particularly in
NiMnSn where it reaches a value of 20 JkgK
for a field of 5T. We substitute Ni with Fe and Co in this alloy, each in
amounts of 1 at% and 3 at% to perturb the electronic concentration and examine
the resulting changes in the magnetocaloric properties. Increasing both Fe and
Co concentrations causes the martensitic transition temperature to decrease,
whereby the substitution by Co at both compositions or substituting 1 at% Fe
leads to a decrease in the magnetocaloric effect. On the other hand, the
magnetocaloric effect in the alloy with 3 at% Fe leads to an increase in the
value of the entropy change to about 30 JkgK at 5T.Comment: 5 pages, 7 figures. Accepted for publication in the Journal of
Applied Physic
Acoustic emission across the magnetostructural transition of the giant magnetocaloric Gd5Si2Ge2 compound
We report on the existence of acoustic emission during the
paramagnetic-monoclinic to ferromagnetic-orthorhombic magnetostructural phase
transition in the giant magnetocaloric Gd5Si2Ge2 compound. The transition
kinetics have been analyzed from the detected acoustic signals. It is shown
that this transition proceeds by avalanches between metastable states.Comment: 5 pages, 4 figure
Relevancia de los diferentes momentos del juego y de las acciones a balón parado (ABP) en los rendimientos del FC Barcelona y Real Madrid durante la liga nacional de fútbol profesional 2011/12
El estudio se centra en la relevancia de las fases dinámicas y estáticas en los rendimientos del FC Barcelona y Real Madrid. Utilizamos la metodologÃa observacional con el fin de tratar de asociar los diferentes Momentos o Fases del juego (MJ) y las Acciones a Balón Parado (ABP) con la obtención de cada uno de los goles. Para conseguirlo, hemos creado un instrumento de observación ad hoc (IOX) y hemos utilizado dos instrumentos de registro (LINCE y MOTS). Para el análisis de los datos del registro y la obtención de resultados, hemos utilizado las técnicas de comparación de proporciones con el software Statgraphics, habiendo encontrado, inicialmente, diferencias significativas entre los dos equipos únicamente en la fase defensiva
Magnetization easy-axis in martensitic Heusler alloys estimated by strain measurements under magnetic-field
We study the temperature dependence of strain under constant magnetic-fields
in Ni-Mn based ferromagnetic Heusler alloys in the form Ni-Mn- (: Ga, In,
Sn, Sb) which undergo a martensitic transformation. We discuss the influence of
the applied magnetic-field on the nucleation of ferromagnetic martensite and
extract information on the easy-axis of magnetization in the martensitic state.Comment: 3 pages, 3 figures. Accepted for publication in Applied Physics
Letter
Lattice dynamics and phonon softening in Ni-Mn-Al Heusler alloys
Inelastic and elastic neutron scattering have been used to study a single
crystal of the NiMnAl Heusler alloy over a broad
temperature range. The paper reports the first experimental determination of
the low-lying phonon dispersion curves for this alloy system. We find that the
frequencies of the TA modes are relatively low. This branch exhibits an
anomaly (dip) at a wave number , which softens with
decreasing temperature. Associated with this anomalous dip at , an
elastic central peak scattering is also present. We have also observed
satellites due to the magnetic ordering.Comment: 6 pages, 6 figures. Accepted for publication in the Physical Review
Rellevà ncia dels diferents moments del joc (mj) i de les accions a balò parat (abp) en el rendiment del FC Barcelona i Reial Madrid durant la lliga nacional de futbol professional 2011/12
L'estudi se centra en la rellevà ncia de les fases dinà miques i està tiques en els rendiments del FC Barcelona i Real Madrid. Utilitzem la metodologia observacional per tal de tractar d'associar els diferents Moments o Fases del joc (MJ) i les Accions a Baló Parat (ABP) amb l'obtenció de cadascun dels gols. Per aconseguir-ho, hem creat un instrument d'observació ad-hoc (IOX) i hem utilitzat dos instruments de registre (LINCE i MOTS). Per a l'anà lisi de les dades del registre i l'obtenció de resultats, hem utilitzat les tècniques de comparació de proporcions amb el programari Statgraphics, havent trobat, inicialment, diferències significatives entre els dos equips únicament en la fase defensiva
Temperature and magnetic field dependences of the elastic constants of Ni-Mn-Al magnetic Heusler alloys
We report on measurements of the adiabatic second order elastic constants of
the off-stoichiometric NiMnAl single crystalline Heusler
alloy. The variation in the temperature dependence of the elastic constants has
been investigated across the magnetic transition and over a broad temperature
range. Anomalies in the temperature behaviour of the elastic constants have
been found in the vicinity of the magnetic phase transition. Measurements under
applied magnetic field, both isothermal and variable temperature, show that the
value of the elastic constants depends on magnetic order, thus giving evidence
for magnetoelastic coupling in this alloy system.Comment: 7 pages, 5 figures. Accepted for publication in Physical the Review
- …