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1.
The magnetic susceptibility of Al2REM (REM = Gd, Dy, and Ho) intermetallic compounds is experimentally investigated by the Faraday method in a wide temperature
interval (290–2000 K) in different magnetic fields (0.3–1.3 T). In the crystalline state, the temperature dependences of the
susceptibility follow the generalized Curie–Weiss law. In the liquid phase, the magnetic susceptibility of these intermetallic
compounds above the melting point increases for all examined samples. The parameters of the electronic structure of the compounds
are calculated based on the experimental data. It is established that the effective magnetic moment per rareearth metal atom
is smaller than that characteristic of the free REM+ ion. 相似文献
2.
J. Dubowik I. Gościańska Y. Kudryavtsev 《The European physical journal. Special topics》2008,158(1):113-118
We report on FMR experiments performed for the first time on thin Ni-Mn-Ga films clamped to the mica substrates and then fully
released from them. The aim is to evaluate the role of magnetoelastic coupling in stressed Ni-Mn-Ga Heusler alloy films that
undergo martensitic transformation. The experimental results show that the difference in the effective magnetization 4π(Meff tubes-Meff films) is negligible in the austenite phase and it increases to about 1–1.5 kG at temperatures well below the martensitic transformation.
The data suggests that magnetoelastic coupling in the martensite phase of Ni-Mn-Ga thin films is typical of normal thin magnetic
films with magnetostriction of about 50 ppm. 相似文献
3.
F. Mallamace C. Branca M. Broccio C. Corsaro N. Gonzalez-Segredo J. Spooren H. E. Stanley S.-H. Chen 《The European physical journal. Special topics》2008,161(1):19-33
This article presents an overview of recent experiments
performed on transport properties of water in the deeply supercooled
region, a temperature region of fundamental importance in the science of water.
We report data of nuclear magnetic resonance, quasi-elastic neutron scattering,
Fourier-transform infrared spectroscopy, and Raman spectroscopy, studying
water confined in nanometer-scale environments. When contained within small
pores, water does not crystallise, and can be supercooled well below its
homogeneous nucleation temperature Th. On this basis it is possible to
carry out a careful analysis of the well known thermodynamical anomalies of
water. Studying the temperature and pressure dependencies of water
dynamics, we show that the liquid-liquid phase transition (LLPT) hypothesis
represents a reliable model for describing liquid water. In this
model, water in the liquid state is a mixture of two different local
structures, characterised by different densities, namely the low density
liquid (LDL) and the high-density liquid (HDL). The LLPT line should terminate
at a special transition point: a low-T liquid-liquid
critical point. We discuss the following experimental findings on
liquid water: (i) a crossover from non-Arrhenius behaviour
at high T to Arrhenius behaviour at low T in transport parameters;
(ii) a breakdown of the Stokes-Einstein relation;
(iii) the existence of a Widom line, which is the
locus of points corresponding to maximum correlation length in the p-T phase
diagram and which ends in the liquid-liquid critical point; (iv) the direct
observation of the LDL phase; (v) a
minimum in the density at approximately 70 K below the
temperature of the density maximum. In our opinion these results represent
the experimental proofs of the validity of the LLPT hypothesis. 相似文献
4.
H. Roy-Poulsen E. Johnson A. Johansen L. Sarholt-Kristensen H. Hayashi 《Hyperfine Interactions》1986,29(1-4):1201-1204
Martensitic transformations have been analysed in a series of antimony implanted austenitic stainless steels using CEMS. The
implanted samples contain about 70 vols martensite, which is considerably more than can be formed conventionally by plastic
deformation or cooling below the martensite start temperature. CEM spectra from implantation induced martensite and from martensite
formed in conventional processes are virtually identical. In both cases the hyperfine field is ≈ 25T. 相似文献
5.
Summary In this work we report on the anisotropic physical properties of silver-sheathed Bi-2223 tapes fabricated by means of hot
extrusion and repeated pressing and sintering processes. The obtained Bi-2223/Ag short tapes, having critical current densitiesJ
c of 20–30 kA/cm2 at 77 K, 0 T, were measured in external magnetic fields up to 0.5T applied in two different orientations (i.e. μ0H‖(a,b)-planes and μ0H ⊥(a,b)-planes). The magnetic characterizations were performed in a wide range of temperatures and magnetic fields to study
the first magnetization curve of tapes evaluating the lower critical fields μ0Hc1⊥ab and ⊥0Hc1#x2016;ab and their dependences on temperature. TheJ
c values at different fields in the temperature range 4.6–90 K, calculated from the magnetization data by the critical state
model, are also presented.
Paper presented at the ?VII Congresso SATT?, Torino, 4–7 October 1994. 相似文献
6.
H. Huth A. A. Minakov A. Serghei F. Kremer C. Schick 《The European physical journal. Special topics》2007,141(1):153-160
A differential AC-chip calorimeter capable to measure the
glass transition in nanometer thin films is described. Due to the
differential setup pJ/K sensitivity is achieved. Heat capacity can
be measured for sample masses below one nanogram even above room
temperature as needed for the study of the glass transition in
nanometer thin polymeric films. The calorimeter allows for the
frequency dependent measurement of complex heat capacity in the
frequency range from 1 Hz to 1 kHz. The glass transition in thin
films of polystyrene (PS) (100–4 nm) and polymethylmethacrylate
(PMMA) (400–10 nm) was determined at well defined experimental
time scales. No thickness dependency of the glass transition
temperature was observed within the error limits (±3 K) -
neither at constant frequency nor for the traces in the activation
diagrams (1 Hz–1 kHz). 相似文献
7.
D. San Martín K.W.P. Aarts P.E.J. Rivera-Díaz-del-Castillo N.H. van Dijk E. Brück S. van der Zwaag 《Journal of magnetism and magnetic materials》2008
This work concerns an in situ study of the isothermal formation of martensite in a stainless steel under the influence of magnetic fields up to 9 T at three different temperatures (213, 233 and 253 K). It is shown that the presence of a constant applied magnetic field promotes the formation of martensite significantly. The activation energy for the nucleation of martensite has been derived using a semi-empirical kinetic model. The experimental results have been analyzed using the Ghosh and Olson model. While this model describes the time and field dependences of the experimental data well, the thermal frictional energy and the defect size values are much lower than those expected from earlier work. 相似文献
8.
L. G. Bujoreanu V. Dia S. Stanciu M. Susan C. Baciu 《The European physical journal. Special topics》2008,158(1):15-20
Free- and constrained recovery behaviors of a Fe-23.3 Mn-2.8 Si (wt.%) Shape Memory Alloy (SMA) were revealed by uncoiling
experiments and tensile tests, respectively. With the enhancement of plastic deformation degree, including by additionally
elongating the hot rolled specimens, the increase of the amount of ε stress induced martensite (SIM) plates in the detriment
if γ austenite, was emphasized by means of optical microscopy and XRD. The tensile-stress variation was analyzed during complex
cycling by constrained recovery of the alloy under study, with a tensile strength of 670 MPa and an ultimate strain of 8%.
The cycles were composed of: (i) room temperature (RT) loading; (ii) RT partial unloading; (iii) constant strain heating and
(iv) constant strain cooling to RT. During the cycles, characterized by average maximum stresses above 500 MPa and recovery
stresses above 260 MPa, the observed stress-temperature evolution confirmed the four stage stress variation reported in literature
[Z.Z. Dong et al., Acta Mater. 53, 4009 (2005)]. In order to maintain the above stress levels, constrained-recovery strain had to be increased with an average
of 1.1% per cycle, between 1 and 3%. 相似文献
9.
V. Sánchez-Alarcos V. Recarte J. I. Pérez-Landazábal C. Gómez-Polo V. A. Chernenko M. A. González 《The European physical journal. Special topics》2008,158(1):107-112
Ferromagnetic Fe-Pd shape memory alloys (SMA) undergo a
martensitic phase transformation during cooling from a parent FCC phase to a
tetragonal FCT martensite. This transformation is thermoelastic and
reversible giving rise to the shape memory effect. On further cooling an
irreversible FCT to BCT transformation occurs that makes impossible the
memory effect. Nevertheless, the transformation from reversible to
irreversible phase has been not complete since a volume fraction of
reversible phase in the alloy is retained even after cooling below the
temperature of appearance of the irreversible phase. The addition of Co
lowers the temperature of the reversible and irreversible phase
transformations but also reduces the amount of transformed irreversible
martensite after cooling to 10 K. 相似文献
10.
Martensitic transformations are extensively influenced by external fields, such as temperature and uniaxial stress, in transformation temperatures, crystallography and amount and morphology of the product martensites. Therefore, to clarify the effect of external fields on martensitic transformations it is very important to understand the essential problems of the transformation, such as thermodynamics, kinetics and the origin of the transformation, whose information is naturally useful in technological applications using the transformation. Magnetic field and hydrostatic pressure are important in such external fields because there exist some significant differences in magnetic moment and atomic volume between the parent and martensitic states. In the present paper, therefore, we summarizz the effects of magnetic field and hydrostatic pressure on martensitic transfonnations in some ferrous and non-ferrous alloys by referring to past and recent works made by our group and many other researchers. The transformation start temperatures of all the ferrous alloys examined increase with increasing magnetic field, but those of non-ferrous alloys, such as Ti-Ni and Cu-Al-Ni shape memory alloys, are not affected. On the other hand, the transformation start temperature decreases with increasing hydrostatic pressure in some ferrous alloys, but increases in Cu-Al-Ni alloys. The magnetic field and hydrostatic pressure dependencies of the martensitic start temperature are in good agreement with those calculated by our proposed equations. During investigations of ferrous Fe-Ni-Co-Ti shape memory alloy, we found that a magnetoelastic martensitic transformation appears and, in addition, several martensite plates grow nearly parallel to the direction of the applied magnetic field in a specimen of Fe-Ni alloy single crystal. We further found that the isothermal process in Fe-Ni-Mn alloy changes to athermal under a magnetic field and the athermal process changes to isothermal under hydrostatic pressure. Based on these facts, a phenomenological theory has been constructed, which unifies the two transformation processes. 相似文献
11.
T. Goryczka J. Lelatko B. Górka-Kostrubiec P. Ochin H. Morawiec 《The European physical journal. Special topics》2008,158(1):131-136
Off-stoichiometric Ni-Mn-Ga alloys, with various chemical compositions, were produced by melt-spinning technique. Transformation
behavior was studied by means of differential scanning calorimetery (DSC). Ribbons and bulks reveal reversible martensitic
transformation which occurs, dependently on chemical composition, in the range of temperatures: between 100°C and -150°C.
Transmission electron microscope and X-ray diffractometer were used for structure examination. Dependently on chemical composition
five-layered (10 M) or seven-layered (14 M) martensite was observed, whereas the parent phase shows the B2 structure. Due
to high cooling rate realized in melt-spinning technique some amount of amorphous phase was found. For all ribbons magnetization
was measured versus change of temperature as well as magnetic field. Due to relatively high density of dislocations lower
value of magnetization were obtained. 相似文献
12.
A. S. Paula K. K. Mahesh F. M. Braz Fernandes 《The European physical journal. Special topics》2008,158(1):45-51
The phase transformations associated with Shape Memory Effect
(SME) can be one step, B19' (martensite) ↔ B2 (austenite),
or two/multiple steps which include the intermediate R phase, depending on
the thermal and thermomechanical history of the alloy. The transformation
temperatures are generally observed above room temperature in Ti-rich Ni-Ti
alloys, while those observed in Ni-rich alloys occur below room temperature.
The goal of the present work is to investigate the phase transformations
evolution in Ti-Rich Ni-Ti SMA (Ni-51 at % Ti) when subjected to two
distinct thermal treatments (500°C for 30 minutes in air and 800°C
for 300 minutes in vacuum) and subsequently multiple steps of marforming
thermomechanical treatments intercalated with thermal treatments (500°C
for 30 minutes in air) and subsequent four distinct final thermal treatments
(400, 450, 500 or 600°C for 30 minutes in air). Further, the stability
of phase transformations in the initial ten thermal cycles of these
thermomechanically treated samples is also studied. Differential Scanning
Calorimetry (DSC) and X-Ray Diffraction (XRD) were used to identify the
transformation temperatures and the phases that are present after the
thermomechanical treatments. 相似文献
13.
D. Auernhammer M. Schmitt M. Ohtsuka M. Kohl 《The European physical journal. Special topics》2008,158(1):249-254
The technologies of electron beam lithography, dry
etching and systems integration are investigated to fabricate a series of
Ni-Mn-Ga double-beam structures designed with decreasing critical dimensions
of 10 μm, 1 μm and 400 nm. Ni-Mn-Ga thin films of 1 μm
thickness are deposited by magnetron sputtering and heat-treated in
free-standing condition after selective removal of the substrate.
Differential scanning calorimetry and electrical resistance measurements on
the films show the characteristic features of martensitic transformation
above room temperature. First optical beam deflection experiments
demonstrate the magnetic and thermal actuation performance of the
double-beam structures. 相似文献
14.
N. V. Rama Rao R. Gopalan V. Chandrasekaran K. G. Suresh 《Applied Physics A: Materials Science & Processing》2010,99(1):265-270
Low field inverse magnetocaloric effect (IMCE) associated with first-order martensitic transition in Ni50−x
Mn37+x
In13 (x=3,4,5) alloys was investigated. By tuning the composition of Ni/Mn, large change in the magnetization occurring between martensite
and austenite phases in a narrow temperature interval was achieved, which results in large IMCE. Under low magnetic field
change of 2 T, a large positive magnetic entropy change (ΔS
M
) of 23.5 J/kg K with a net refrigeration capacity of 53 J/kg was obtained near room temperature (308 K) in the x=3 alloy. The results show that a small variation in Ni/Mn ratio significantly influences the martensitic transition temperature
and the associated magnetic and magnetocaloric properties. 相似文献
15.
Fannin PC Malaescu I Marin CN Stefu N 《The European physical journal. E, Soft matter》2008,27(2):145-148
This paper reports on the frequency dependence of the magnetic and electric power dissipation in a magnetic fluid sample,
in the microwave frequency range (0.5 to 8GHz), at various values of the static magnetic field (0 to 167.8kA/m). The computation
of the power dissipation relies on the experimental values measured for the complex dielectric permittivity, ɛ = ɛ′ - iɛ″, and the complex magnetic permeability, μ = μ′ - iμ″, over the same frequency range. The results show that the magnetic power dissipation is much larger than the electric one
for the investigated sample. At a specific frequency, f (Hz) , the power dissipation, p, depends on the external magnetic field, and exhibits a maximum. The result obtained suggests the possibility of controlling
the energy absorption in the microwave range by means of the application of an external magnetic field. 相似文献
16.
D. R. Lee S. H. Choi H. H. Lee J.-Y. Kim C.-J. Yu 《The European physical journal. Special topics》2009,167(1):163-169
We studied ~0.5 μm and 30–80 ? thick films of a normal dielectric
liquid, tetrakis(2-ethylhexoxy)silane (TEHOS), at temperature range 228–286 K,
deposited onto silicon (111) substrate with native oxide using X-ray
reflectivity. TEHOS is spherical with size ~10 ?, non-polar,
non-reactive, and non-entangling; TEHOS has been reported to show interfacial
layering at room temperature and surface layering at 0.23 Tc (Tc≈
950 K). For films m thick, the reflectivity data did not change
significantly as a function of temperature; for films 30–80 ? thick, the
reflectivity data did change. The data could be fitted with an electron density
model composed of a minimum necessary number of Gaussians and a uniform density
layer with error-function broadened interfaces. When the film thickness is 60–80 ? below 246 K, we found that the interface
and the surface layering coexist
but do not overlap. When the film thickness is 30–40 ? below 277 K, they
overlap and the electron density profile shows slowly decreasing molecular
oscillations at the air-liquid interface. 相似文献
17.
T. Eimüller P. Fischer M. Köhler M. Scholz P. Guttmann G. Denbeaux S. Glück G. Bayreuther G. Schmahl D. Attwood G. Schütz 《Applied Physics A: Materials Science & Processing》2001,73(6):697-701
X-ray magnetic circular dichroism (X-MCD) was used as a large, element-specific and quantitative magnetic contrast mechanism
in the soft X-ray microscopes at BESSY I (Berlin) and the ALS (Berkeley). The present state and potential of magnetic transmission
X-ray microscopy (MTXM) is outlined. The possibility to record images in varying magnetic fields and the high spatial resolution
down to 25 nm were used to image out-of-plane magnetized (4 ?Fe / 4 ?Gd)×75 systems. Magnetic domains could be studied in
arrays of circular and square dots with lateral dimensions down to 180 nm. Hysteresis loops of individual dots were deduced
using the direct proportionality of the X-MCD contrast to the sample magnetization. Images of a 3 nmCr / 50 nmFe / 6 nmCr
film demonstrate for the first time that MTXM is also able to observe in-plane magnetized domains. In the future the possible
applications of MTXM will be extended with regard to the strength of the external field, the available energy range and the
sample conditions by building a dedicated transmission X-ray microscope for magnetic imaging at BESSY II.
Received: 22 May 2001 / Accepted: 4 July 2001 / Published online: 5 October 2001 相似文献
18.
H. Morawiec T. Goryczka J. Lelatko K. Prusik A. Drdzeń 《The European physical journal. Special topics》2008,158(1):93-98
Deformation of polycrystalline Ni-Mn-Ga alloys was
studied for both the L21 parent phase and 10 M martensitic state. The
effect of deformation by compression up to the fracture on mechanical
behavior and structure change was studied for the inhomogeneous as-cast
state and after annealing at 900○C for 50 hours. The structure, after
deformation of the parent phase, observed by TEM reveals the presence of 10 M
and 14 M martensite in the matrix, whereas the deformation of 10 M martensite
does not show the change of the structure type. The stress-strain curves
were analyzed and compared with the earlier published results. 相似文献
19.
J. Balogh D. Kaptás L. F. Kiss T. Kemény I. Vincze K. Temst C. Van Haesendonck 《Hyperfine Interactions》2005,165(1-4):49-53
An (0.2 nm 57Fe / 2.6 nm Ag)75 granular multilayer sample and heterostructures with additional continuous Fe layers in different sequences were studied
in magnetic field applied at different temperatures. The broadening of the superparamagnetic lines was found to be very similar
for the three samples in applied fields both parallel and perpendicular to the sample plane. While the layer sequence has
no significant effect on the superparamagnetic properties, the continuous magnetic layers follow a different approach to saturation
in perpendicular magnetic fields. 相似文献
20.
M. Chmielus V. A. Chernenko W. B. Knowlton G. Kostorz P. Müllner 《The European physical journal. Special topics》2008,158(1):79-85
Magneto-mechanical experiments with a rotating magnetic field of 0.97 T were performed with a Ni-Mn-Ga single crystal. Periodic
strains exceeding 1% were recorded over a hundred million magneto-mechanical cycles. The twin microstructure of the cycled
crystal was characterized using atomic force microscopy (AFM) and magnetic force microscopy (MFM). In the center of the sample,
no twin boundaries were found. At the sample edges, the microstructure shows a dense twin pattern. The results are compared
with previous experiments of differently trained crystals. It is useful to distinguish between “ineffective training”, which
results in a nearly self-accommodated martensite, and “effective training”, which results in a nearly single-variant crystal.
The evolution of twin structure is discussed in terms of training, magneto-mechanical cycling, and extrinsic constraints imposed
by the experimental setting. It is concluded that the response of a magnetic shape memory alloy to an alternating excitation
depends strongly on the initial twin microstructure established through training. In particular, ineffective training results
in a twin microstructure which can adapt to extrinsic constraints resulting in continued large periodic magnetic-field-induced
deformation. In contrast, the twin microstructure of an effectively trained crystal can not adapt to extrinsic constraints
resulting in early failure by fracture. 相似文献