Calorimetric and acoustic emission study of the premartensitic and martensitic transitions in Ni–Mn–Ga

Pérez‐Reche, Francisco J.; Vives, Eduard; Mañosa, Lluı́s; Planes, Antoni

doi:10.1016/j.msea.2003.10.360

Cited by 12 publications

(11 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Therefore, the exponents show that higher fields lead to signals of smaller amplitudes and energies with shorter durations. It is worth noticing that in case of the amplitude a zero field exponent ␣ = 2.3Ϯ 0.15 has been reported, 19 which is in good agreement with our results. The zero-field exponents are listed in Table II.…”

Section: Figure 3͑a͒supporting

confidence: 93%

“…18 In the present case, AE is known to be associated with the transition mechanism that involves shuffles consisting of shifts of ͑110͒ planes in the ͓110͔ direction with a periodicity of three atomic planes. 19 Actually, monitoring the transition by AE measurements reveals a twofold advantage. On the one hand, AE is very sensitive to structural changes occurring in the system and, on the other hand, it provides valuable information related to transition dynamics.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Premartensitic transition inNi2MnGaHeusler alloys: Acoustic emission study

et al. 2009

Self Cite

View full text Add to dashboard Cite

This paper deals with the study of the acoustic emission generated during the intermediate ͑premartensitic͒ transition to a micromodulated phase that precedes the martensitic transition in a nearly stoichiometric ferromagnetic Heusler Ni 52 Mn 23 Ga 25 crystal under applied magnetic fields. In the range of applied fields, the field stabilizes the high-temperature cubic phase by shifting the transition to lower temperatures. At low fields the amplitude, energy, and duration distributions of the acoustic emission events show power-law behavior which reflect the absence of characteristic scales associated with the transition. The corresponding exponents increase with the applied field, which indicate a weakening of the first-order character of the transition. No acoustic emission has been detected above ϳ2.5 kOe which is close to the field at which magnetic saturation is reached.

show abstract

Section: Figure 3͑a͒supporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Premartensitic transition inNi2MnGaHeusler alloys: Acoustic emission study

et al. 2009

Self Cite

View full text Add to dashboard Cite

show abstract

“…Resistivity measurements were made on the PPMS using an ac technique. The specific-heat data show a broad peak centered at T = 225 K in agreement with previous measurements in a sample of the same composition [21]. This feature does not have any measurable thermal hysteresis associated with it.…”

supporting

confidence: 90%

Combined Experimental and Theoretical Investigation of the Premartensitic Transition inNi2MnGa

et al. 2008

View full text Add to dashboard Cite

Ultraviolet-photoemission (UPS) measurements and supporting specific-heat, thermal-expansion, resistivity and magnetic-moment measurements are reported for the magnetic shape-memory alloy Ni2MnGa over the temperature range 100 K < T < 250 K. All measurements detect clear signatures of the premartensitic transition (TPM ∼ 247 K) and the martensitic transition (TM ∼ 196 K). Temperature-dependent UPS shows a dramatic depletion of states (pseudogap) at TPM located 0.3 eV below the Fermi energy. First-principles electronic structure calculations show that the peak observed at 0.3 eV in the UPS spectra for T > TPM is due to the Ni-d minority-spin electrons. Below TM this peak disappears, resulting in an enhanced density of states at energies around 0.8 eV. This enhancement reflects Ni-d and Mn-d electronic contributions to the majority-spin density of states and is accompanied by significant reconstruction of the Fermi surface. [5] as a system undergoing a martensitic transition (MT) in its ferromagnetic phase (T C ∼ 380 K) with little magnetic hysteresis. In the last decade research on these alloys has focused on the structural and magnetic characterization and on their shape-memory applications [6]. First-principles calculations [7,8] and measurements on shape-memory alloys [9,10,11,12] indicate the driving role of the electronic structure and its relation to the lattice dynamics.The lattice dynamics of Ni 2 MnGa has been investigated from ultrasonic measurements [13] and neutron diffraction experiments [14,15,16]. It was found that the transverse TA 2 phonon branch exhibits pronounced softening at 1/3 of the zone boundary on decreasing the temperature, and this softening was described as a Bain distortion in the context of the Wechler, Lieberman, and Read theory of martensite formation [17]. In similar structural shape-memory alloys InTl [9], AuZn [10] and NiAl [11], this softening is associated with nesting features of the Fermi surface [8]. Below a certain temperature, there is a freezing of the displacements associated with this soft phonon so that a micro-modulated phase forms, which is described as a periodic distortion of the parent cubic phase [14]. In Ni 2 MnGa, the premartensitic phase develops with little or no thermal hysteresis and is driven by a magnetoelastic coupling [18]. On further cooling, Ni 2 MnGa transforms to an approximately fivelayered quasi-tetragonal martensitic structure. The lowtemperature phase is incommensurate [14] with a period (0.43,0.43,0) and exhibits well-defined phasons best characterized as charge-density wave (CDW) excitations [16].In this paper we study the role of conduction electrons in the two-step MT in Ni 2 MnGa using photoemission spectroscopy and thermodynamic measurements. LEED and X-ray diffraction Laue measurements show the quality of our sample is appropriate for high-resolution photoemission spectroscopy. Ultraviolet photoemission (UPS) measurements show the opening of a pseudogap at 0.3 eV below the Fermi energy at the MT and provide further evidence that the Fer...

show abstract

“…What is more, the present scheme of plasticity does not require ad-hoc procedures for the nucleation and annihilation of dislocations, as in discrete dislocation dynamics [30]. When, in contrast, the variable d can be neglected in the original setting, as in weak martensitic transformations (or in magnetics), the model still generates several decades of powerlaw avalanche distribution in accordance with the experiments in Ni-Mn-Ga [4], but only in the presence of some quenched disorder represented again by a Gaussian distribution of δ i in the initial configuration. In this case the emergence of limited scaling does not involve training, and can be explained by the proximity of the system to a classical critical point [12].…”

supporting

confidence: 63%

“…We reproduce all the principal observations in thermally driven martensites, including power-law statistics, hysteresis shakedown, asymmetric signal shapes, and correlated disorder. PACS numbers: 62.20.Fe,64.60.My,81.30.Kf,89.75.Fb Experiments in martensites reveal intermittent behavior with power-law statistics [1,2,3,4], showing an intrinsic complexity comparable to that of turbulence, earthquakes, internet networks, and financial markets. Criticality is known to be an issue of great significance in contemporary science, giving a framework for understanding the emergence of complexity in a variety of natural systems [5,6].…”

mentioning

confidence: 99%

Training-Induced Criticality in Martensites

Pérez‐Reche

Truskinovsky²,

Zanzotto³

2007

Phys. Rev. Lett.

View full text Add to dashboard Cite

We propose an explanation for the self-organization towards criticality observed in martensites during the cyclic process known as 'training'. The scale-free behavior originates from the interplay between the reversible phase transformation and the concurrent activity of lattice defects. The basis of the model is a continuous dynamical system on a rugged energy landscape, which in the quasi-static limit reduces to a sandpile automaton. We reproduce all the principal observations in thermally driven martensites, including power-law statistics, hysteresis shakedown, asymmetric signal shapes, and correlated disorder. PACS numbers: 62.20.Fe,64.60.My,81.30.Kf,89.75.Fb Experiments in martensites reveal intermittent behavior with power-law statistics [1,2,3,4], showing an intrinsic complexity comparable to that of turbulence, earthquakes, internet networks, and financial markets. Criticality is known to be an issue of great significance in contemporary science, giving a framework for understanding the emergence of complexity in a variety of natural systems [5,6]. Within materials science, criticality has been recognized in the last years as a key factor in crystal plasticity, brittle fracture and damage [7]. In the present paper we develop a model explaining why similar behavior is also observed in martensitic transformations.Reversible martensitic transformations involve a coordinated distortion of the crystal lattice and belong to the class of ferroelastic first-order phase changes with athermal character [8,9]. In such systems the macroscopic strain discontinuity typically splits into a set of bursts (avalanches) corresponding to transitions between neighboring metastable states. The individual avalanches can be detected through the measurement of the intermittent acoustic or calorimetric signals. The size distribution observed in shape-memory alloys (Cu-Al-Ni, Cu-ZnAl, Cu-Al-Mn, Ni-Mn-Ga) was shown to be scale free [1,2,3,4,9]. Despite the apparent similarity with driven ferromagnetic systems, where the scale-free Barkhausen noise has been known for a long time, the experiments on memory alloys show features not observed in magnets, and which are instead reminiscent of plastic shakedown. In particular, the critical character of the avalanches [2,3] and the smoothing of the hysteresis profile [3, 10] emerge only after multiple thermal cycling through the transition.The mechanism leading to training-induced critical behavior in martensites strongly resembles the phenomenology associated with self-organized criticality (SOC) [5]. The SOC paradigm in the form of a sandpile automaton has been applied to martensitic transformations in 11; which however, lacked a connection to the physics of martensitic transformations. A different set of models exploited the similarity between martensites and magnetics by interpreting both in an Ising-type framework, with zero temperature and quenched disorder [12]. In this context the power-law over a few decades of avalanche sizes is viewed as a sign of proximity of the system to a ...

show abstract

Calorimetric and acoustic emission study of the premartensitic and martensitic transitions in Ni–Mn–Ga

Cited by 12 publications

References 14 publications

Premartensitic transition inNi2MnGaHeusler alloys: Acoustic emission study

Premartensitic transition inNi2MnGaHeusler alloys: Acoustic emission study

Combined Experimental and Theoretical Investigation of the Premartensitic Transition inNi2MnGa

Training-Induced Criticality in Martensites

Contact Info

Product

Resources

About