Comparing properties of substrate-constrained and freestanding epitaxial Ni–Mn–Ga films

Backen, Anja; Yeduru, S.R.; Kohl, Manfred; Baunack, S.; Diestel, Anett; Holzäpfel, B.; Schultz, L.; Fähler, S.

doi:10.1016/j.actamat.2010.02.016

Cited by 78 publications

(42 citation statements)

References 24 publications

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“…Today large efforts are carried out to develop MIRactive Ni-Mn-Ga films because of their promising applications as new micro-actuators or micro-sensors for micro-electro-mechanical systems (MEMSs) [3,4,9,17,18]. Highest strains being only reported in bulk single crystals, epitaxial growth is considered to be the most promising process.…”

Section: Introductionmentioning

confidence: 99%

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Tuning macro-twinned domain sizes and the b-variants content of the adaptive 14-modulated martensite in epitaxial Ni–Mn–Ga films by co-sputtering

Tillier¹,

Bourgault²,

Odier³

et al. 2011

Acta Materialia

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In order to obtain modulated martensite in our epitaxial Ni-Mn-Ga films, we tuned the composition by using a co-sputtering process.Here we present how the composition affects the variant distribution of the 14-modulated martensite at room temperature. The nature of such modulated martensites is still strongly debated for magnetic shape memory alloys. It has been very recently demonstrated that the modulated martensites in Ni-Mn-Ga are adaptive phases. The results presented here corroborate this theory for the first time, for three different compositions. Moreover, we demonstrate with the help of the adaptive modulations theory that b-variants of the 14-modulated martensite form close to the free surface of the film to release the stress induced by branching of macro-twinned domains during the martensitic transformation on a rigid substrate. At room temperature, the content of such b-variants is found to strongly decrease when the macro-twinned domain sizes increase.

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Section: Introductionmentioning

confidence: 99%

“…Tuning the composition of Ni-Mn-Ga films has been achieved by means of various techniques like changing the target composition [3], the deposition temperature [4], the sputtering reactor pressure [20] or applying a negative bias voltage on the substrate [21].…”

Section: Introductionmentioning

confidence: 99%

Tuning macro-twinned domain sizes and the b-variants content of the adaptive 14-modulated martensite in epitaxial Ni–Mn–Ga films by co-sputtering

Tillier¹,

Bourgault²,

Odier³

et al. 2011

Acta Materialia

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“…[16,27,28]. MSM in thin films can be recognized by a sharp decrease in magnetization when a magnetic field is applied in the plane of the film because the phase transition is accompanied by a change in the easy direction of magnetization.…”

Section: Shape Memorymentioning

confidence: 99%

Magnetic spectroscopy and microscopy of functional materials

Jenkins

2011

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Mainz, 2011 SummaryHeusler intermetallics Mn 2 Y Ga and X 2 MnGa (X, Y =Fe, Co, Ni) undergo tetragonal magnetostructural transitions that can result in half metallicity, magnetic shape memory, or the magnetocaloric effect. Understanding the magnetism and magnetic behavior in functional materials is often the most direct route to being able to optimize current materials for todays applications and to design novel ones for tomorrow.Synchrotron soft x-ray magnetic spectromicroscopy techniques are well suited to explore the the competing effects from the magnetization and the lattice parameters in these materials as they provide detailed element-, valence-, and site-specific information on the coupling of crystallographic ordering and electronic structure as well as external parameters like temperature and pressure on the bonding and exchange.Fundamental work preparing the model systems of spintronic, multiferroic, and energy-related compositions is presented for context. The methodology of synchrotron spectroscopy is presented and applied to not only magnetic characterization but also of developing a systematic screening method for future examples of materials exhibiting any of the above effects.

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“…This kind of morphology also been observed in other shape memory alloy system e.g. Ni-Mn-Ga. [33][34][35][36][37] The twinning in the films P3 and P4 at RT indicate the presence of a finely twinned room temperature martensite which could not be detected in RT x-ray diffraction studies, that are sensitive to the epitaxial lattice planes parallel to the substrate surface only. The observed morphologies are also evident in the SEM measurements.…”

Section: Microstructural Featuresmentioning

confidence: 99%

Investigations on Ni-Co-Mn-Sn thin films: Effect of substrate temperature and Ar gas pressure on the martensitic transformations and exchange bias properties

Machavarapu

Jakob

2015

AIP Advances

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We report the effect of substrate temperature (TS) and Ar gas pressure (PD) on the martensitic transformations, magnetic and exchange bias (EB) properties in Heusler type Ni-Co-Mn-Sn epitaxial thin films. Martensitic transformation temperatures and EB fields at 5 K were found to increase with increasing TS. The observed maximum EB value of 320 Oe after field cooling in the film deposited at 650 ∘C is high among the values reported for Ni-Mn-Sn thin films which is attributed to the coexistence of ferromagnetic (FM) and antiferromagnetic (AF) phases in the martensitic state. In the case of PD variation, with increase in PD, martensitic transformation temperatures were increased and a sharp transformation was observed in the film deposited at 0.06 mbar. Magnetization values at 5 K were higher for increasing PD. These observations are attributed to the compositional shift. EB effect is also present in these films. Microstructural features observed using atomic force microscopy (AFM) shows a fine twinning and reduced precipitation with increase in PD, which is also confirmed from the scanning electron microscopy (SEM) images. EB effects in both series were confirmed from the training effect. Target ageing effect has been observed in the films deposited before and after ninety days of time interval. This has been confirmed both on substrate temperature and Ar gas pressure variations.

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Comparing properties of substrate-constrained and freestanding epitaxial Ni–Mn–Ga films

Cited by 78 publications

References 24 publications

Tuning macro-twinned domain sizes and the b-variants content of the adaptive 14-modulated martensite in epitaxial Ni–Mn–Ga films by co-sputtering

Tuning macro-twinned domain sizes and the b-variants content of the adaptive 14-modulated martensite in epitaxial Ni–Mn–Ga films by co-sputtering

Magnetic spectroscopy and microscopy of functional materials

Investigations on Ni-Co-Mn-Sn thin films: Effect of substrate temperature and Ar gas pressure on the martensitic transformations and exchange bias properties

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