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Lluis Manosa

Publications and source records attributed to Lluis Manosa.

At least 19 recordsLinked to original sources
arXiv2016

Mechanocaloric effects in Shape Memory Alloys

Shape memory alloys are a class of ferroic materials which undergo a structural (martensitic) transition where the associated ferroic property is a lattice distortion (strain). The sensitiveness of the transition to the conjugated external field (stress), together with the latent heat of the transition gives rise to giant mechanocaloric effects. In non-magnetic shape memory alloys, the lattice distortion is mostly described by a pure shear and the martensitic transition in this family of alloys is strongly affected by uniaxial stress whereas it is basically insensitive to hydrostatic pressure. As a result, non-magnetic alloys exhibit giant elastocaloric effects but negligible barocaloric effects. By contrast, in a number of magnetic shape memory alloys, the lattice distortion at the martensitic transition involves a volume change in addition to the shear strain. Those alloys are affected by both uniaxial stress and hydrostatic pressure and they exhibit giant elastocaloric and barocaloric effects. The paper aims at providing a critical survey of available experimental data on elastocaloric and barocaloric effects in magnetic and non-magnetic shape memory alloys.

cond-mat.mtrl-sci↗
arXiv2014

Barocaloric and Magnetocaloric Effects in Fe49Rh51

We report on calorimetry under applied hydrostatic pressure and magnetic field at the antiferromagnetic (AFM)-ferromagnetic (FM) transition of Fe$_{49}$Rh$_{51}$. Results demonstrate the existence of a giant barocaloric effect in this alloy, a new functional property that adds to the magnetocaloric and elastocaloric effects previously reported for this alloy. All caloric effects originate from the AFM/FM transition which encompasses changes in volume, magnetization and entropy. The strong sensitivity of the transition temperatures to both hydrostatic pressure and magnetic field confers to this alloy outstanding values for the barocaloric and magnetocaloric strengths ($|\Delta S|$/$\Delta p$ $\sim$ 12 J kg$^{-1}$ K $^{-1}$ kbar$^{-1}$ and $|\Delta S|$/$\mu_0\Delta H$ $\sim$ 12 J kg$^{-1}$ K$^{-1}$ T$^{-1}$). Both barocaloric and magnetocaloric effects have been found to be reproducible upon pressure and magnetic field cycling. Such a good reproducibility and the large caloric strengths make Fe-Rh alloys particularly appealing for solid-state cooling technologies at weak external stimuli.

cond-mat.mtrl-sci↗
arXiv2013

Advanced materials for solid-state refrigeration

Recent progress on caloric effects are reviewed. The application of external stimuli such as magnetic field, hydrostatic pressure, uniaxial stress and electric field give rise respectively to magnetocaloric, barocaloric, elastocaloric and electrocaloric effects. The values of the relevant quantities such as isothermal entropy and adiabatic temperature-changes are compiled for selected materials. Large values for these quantities are found when the material is in the vicinity of a phase transition. Quite often there is coupling between different degrees of freedom, and the material can exhibit cross-response to different external fields. In this case, the material can exhibit either conventional or inverse caloric effects when a field is applied. The values reported for the many caloric effects at moderate fields are large enough to envisage future application of these materials in efficient and environmental friendly refrigeration.

cond-mat.mtrl-sci↗
arXiv2009

Lattice dynamics in magnetic superelastic Ni-Mn-In alloys. Neutron scattering and ultrasonic experiments

Neutron scattering and ultrasonic methods have been used to study the lattice dynamics of two single crystals of Ni-Mn-In Heusler alloys close to Ni$_{50}$Mn$_{34}$In$_{16}$ magnetic superelastic composition. The paper reports the experimental determination of the low-lying phonon dispersion curves and the elastic constants for this alloy system. We found that the frequencies of the TA$_{2}$ branch are relatively low and it exhibits a small dip anomaly at a wave number $\xi_{0} \approx 1/3$, which softens with decreasing temperature. Associated with the softening of this phonon, we also observed the softening of the shear elastic constant $C'=(C_{11}-C_{12})/2$. Both temperature softenings are typical for bcc based solids which undergo martensitic transformations and reflect the dynamical instability of the cubic lattice against shearing of $\{110\}$ planes along $<1\bar{1}0>$ directions. Additionally, we measured low-lying phonon dispersion branches and elastic constants in applied magnetic fields aimed to characterize the magnetoelastic coupling.

cond-mat.mtrl-sci↗
arXiv2008

Phase diagram of Fe-doped Ni-Mn-Ga ferromagnetic shape-memory alloys

We have studied the effect of Fe addition on the structural and magnetic transitions in the magnetic shape memory alloy Ni-Mn-Ga by substituting systematically each atomic species by Fe. Calorimetric and AC susceptibility measurements have been carried out in order to study the magnetic and structural transformation properties. We find that the addition of Fe modifies the structural and magnetic transformation temperatures. Magnetic transition temperatures are displaced to higher values when Fe is substituted into Ni-Mn-Ga, while martensitic and premartensitic transformation temperatures shift to lower values. Moreover, it has been found that the electron per atom concentration essentially governs the phase stability in the quaternary system. However, the observed scaling of transition temperatures with $e/a$ differs from that reported in the related ternary system Ni-Mn-Ga.

cond-mat.mtrl-sci↗
arXiv2008

Elastocaloric effect associated with the martensitic transition in shape-memory alloys

The elastocaloric effect in the vicinity of the martensitic transition of a Cu-Zn-Al has been studied by inducing the transition by strain or stress measurements. While transition trajectories show significant differences, the entropy change associated with the whole transformation (\DeltaSt) is coincident in both kind of experiments since entropy production is small compared to \DeltaSt. The values agree with estimations based on the Clausius- Clapeyron equation. The possibility of using these materials for mechanical refrigeration is also discussed.

cond-mat.mtrl-sci↗
arXiv2007

Effects of hydrostatic pressure on the magnetism and martensitic transition of Ni-Mn-In magnetic superelastic alloys

We report magnetization and differential thermal analysis measurements as a function of pressure accross the martensitic transition in magnetically superelastic Ni-Mn-In alloys. It is found that the properties of the martensitic transformation are significantly affected by the application of pressure. All transition temperatures shift to higher values with increasing pressure. The largest rate of temperature shift with pressure has been found for Ni$_{50}$Mn$_{34}$In$_{16}$ as a consequence of its small entropy change at the transition. Such a strong pressure dependence of the transition temperature opens up the possibility of inducing the martensitic transition by applying relatively low hydrostatic pressures.

cond-mat.mtrl-sci↗
arXiv2007

Tailoring magnetic and magnetocaloric properties of martensitic transitions in ferromagnetic Heusler alloys

Ni$_{50}$Mn$_{34}$In$_{16}$ undergoes a martensitic transformation around 250 K and exhibits a field induced reverse martensitic transformation and substantial magnetocaloric effects. We substitute small amounts Ga for In, which are isoelectronic, to carry these technically important properties to close to room temperature by shifting the martensitic transformation temperature.

cond-mat.mtrl-sci↗
arXiv2007

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-$X$ ($X$: 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.

cond-mat.mtrl-sci↗
arXiv2007

Hysteresis in a system driven by either generalized force or displacement variables

We report on experiments aimed at comparing the hysteretic response of a Cu-Zn-Al single crystal undergoing a martensitic transition under strain-driven and stress-driven conditions. Strain-driven experiments were performed using a conventional tensile machine while a special device was designed to perform stress-driven experiments. Significant differences in the hysteresis loops were found. The strain-driven curves show re-entrant behaviour (yield point) which is not observed in the stress-driven case. The dissipated energy in the stress-driven curves is larger than in the strain-driven ones. Results from recently proposed models qualitatively agree with experiments.

cond-mat.mtrl-sci↗
arXiv2007

Effect of Co and Fe on the inverse magnetocaloric properties of Ni-Mn-Sn

At certain compositions Ni-Mn-$X$ Heusler alloys ($X$: group IIIA-VA elements) undergo martensitic transformations, and many of them exhibit inverse magnetocaloric effects. In alloys where $X$ is Sn, the isothermal entropy change is largest among the Heusler alloys, particularly in Ni$_{50}$Mn$_{37}$Sn$_{13}$ where it reaches a value of 20 Jkg$^{-1}$K$^{-1}$ 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 Jkg$^{-1}$K$^{-1}$ at 5T.

cond-mat.mtrl-sci↗
arXiv2007

Magnetic superelasticity and inverse magnetocaloric effect in Ni-Mn-In

Applying a magnetic field to a ferromagnetic Ni$_{50}$Mn$_{34}$In$_{16}$ alloy in the martensitic state induces a structural phase transition to the austenitic state. This is accompanied by a strain which recovers on removing the magnetic field giving the system a magnetically superelastic character. A further property of this alloy is that it also shows the inverse magnetocaloric effect. The magnetic superelasticity and the inverse magnetocaloric effect in Ni-Mn-In and their association with the first order structural transition is studied by magnetization, strain, and neutron diffraction studies under magnetic field.

cond-mat.mtrl-sci↗
arXiv2007

Cooling and heating by adiabatic magnetization in the Ni$_{50}$Mn$_{34}$In$_{16}$ magnetic shape memory alloy

We report on measurements of the adiabatic temperature change in the inverse magnetocaloric Ni$_{50}$Mn$_{34}$In$_{16}$ 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.

cond-mat.mtrl-sci↗
arXiv2006

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 Ni$_{54}$Mn$_{23}$Al$_{23}$ 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.

cond-mat.mtrl-sci↗
arXiv2005

Inverse magnetocaloric effect in ferromagnetic Ni-Mn-Sn alloys

The magnetocaloric effect (MCE) in paramagnetic materials has been widely used for attaining very low temperatures by applying a magnetic field isothermally and removing it adiabatically. The effect can be exploited also for room temperature refrigeration by using recently discovered giant MCE materials. In this letter, we report on an inverse situation in Ni-Mn-Sn alloys, whereby applying a magnetic field adiabatically, rather than removing it, causes the sample to cool. This has been known to occur in some intermetallic compounds, for which a moderate entropy increase can be induced when a field is applied, thus giving rise to an inverse magnetocaloric effect. However, the entropy change found for some ferromagnetic Ni-Mn-Sn alloys is just as large as that reported for giant MCE materials, but with opposite sign. The giant inverse MCE has its origin in a martensitic phase transformation that modifies the magnetic exchange interactions due to the change in the lattice parameters.

cond-mat.mtrl-sci↗
arXiv2004

Driving rate effects in avalanche-mediated, first-order phase transitions

We have studied the driving rate and temperature dependence of the power-law exponents that characterize the avalanche distribution in first-order phase transitions. Measurements of acoustic emission in structural transitions in Cu-Zn-Al and Cu-Al-Ni are presented. We show how the observed behaviour emerges within a general framework of competing time scales of avalanche relaxation, driving rate, and thermal fluctuations. We have confirmed our findings by numerical simulations of a prototype model.

cond-mat.dis-nn↗
arXiv2002

Disorder induced critical phenomena in magnetically glassy Cu-Al-Mn alloys

Measurements of magnetic hysteresis loops in Cu-Al-Mn alloys of different Mn content at low temperatures are presented. The loops are smooth and continuous above a certain temperature, but exhibit a magnetization discontinuity below that temperature. Scaling analysis suggest that this system displays a disorder induced phase transition line. Measurements allow to determine the critical exponents $β=0.03\pm 0.01$ and $βδ= 0.4 \pm 0.1$ in agreement with those reported recently [Berger et al., Phys. Rev. Lett. {\bf 85}, 4176 (2000)]

cond-mat.dis-nn↗