VARIFORC: An optimized protocol for calculating non-regular first-order reversal curve (FORC) diagrams

Egli, Ramón

doi:10.1016/j.gloplacha.2013.08.003

Cited by 249 publications

(280 citation statements)

References 47 publications

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“…This indicates an important caveat in FORC measurements of high concentrations of very high coercivity materials which are typically not encountered in geologic contexts. All FORC diagrams were processed using the VARIFORC function in FORCinel, 22,23 which is written in Igor (V2.02 in IGOR Pro7, WaveMetrics, Portland, OR). In processing the FORC data, the lower edge artifact was removed 24 prior to plotting the FORC diagram.…”

Section: A Theory and Simulationmentioning

confidence: 99%

Multiphase magnetic systems: Measurement and simulation

Cao

Ahmadzadeh

et al. 2018

Journal of Applied Physics

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Multiphase magnetic systems are common in nature and are increasingly being recognized in technical applications. One characterization method which has shown great promise for determining separate and collective effects of multiphase magnetic systems is first order reversal curves (FORCs). Several examples are given of FORC patterns which provide distinguishing evidence of multiple phases. In parallel, a visualization method for understanding multiphase magnetic interaction is given, which allocates Preisach magnetic elements as an input 'Preisach hysteron distribution pattern' (PHDP) to enable simulation of different 'wasp-waisted' magnetic behaviors. These simulated systems allow reproduction of different major hysteresis loop, FORC pattern, and switching field distributions of real systems and parameterized theoretical systems.The experimental FORC measurements and FORC diagrams of four commercially obtained magnetic materials, particularly those sold as nanopowders, shows that these materials are often not phase pure. They exhibit complex hysteresis behaviors that are not predictable based on relative phase fraction obtained by characterization methods such as diffraction. These multiphase materials, Even though the ideal characteristics of hysteresis in perfect single magnetic domains is generally accepted, it is still a challenge to interpret the hysteresis of real materials, as it depends on particle size, shape, and distribution, as well as stress, defects, and impurities. The hysteresis of magnetic mixtures is even more complex, as interactions between non-dilute phases distort the simple loop shape. However, the parameters extracted from major hysteresis loop -for instance, coercivityare not very efficient at showing the interactions of magnetic phases in a multiphase system. First order reversal curve (FORC) analysis is one technique which has developed rapidly in the last two decades, 1 providing a powerful tool for observing magnetic switching contributed by different magnetic phases. FORC is now applied to understand various hysteretic behaviors in metalinsulator transitions, 2 ferroelectricity, 3 magnetocalorics, 4 and perpendicular magnetic recording media. 5 The FORC technique can also be employed to distinguish the different magnetic signals in multiphase systems 4,6 to investigate subtle magnetic features caused by interaction of multiple magnetic phases.In this paper, a series of multiphase magnetic nanopowders are investigated experimentally using major hysteresis loops and FORC diagrams and these systems are also modeled using 'Preisach hysteron distribution patterns' (PHDPs) based on the classical Preisach model (CPM) to aid in descriptive understanding of the reduction of coercivity, or 'wasp-waistedness' features, observed in major loops of multiphase materials. The FORC diagrams of them generally indicate the existence of a low coercivity phase, a high coercivity phase, and a coupling region, which can all be simulated using PHDPs. Together, the simulations and measurements pr...

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Section: A Theory and Simulationmentioning

confidence: 99%

Multiphase magnetic systems: Measurement and simulation

Cao

Ahmadzadeh

et al. 2018

Journal of Applied Physics

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“…FORC diagrams were calculated from [300 FORCs measured on each sample using a saturating field of 2.2 T, time constants of 100-300 ms, field steps of 4-6 mT, and maximum coercivities (B c ) of 1-1.95 T, depending on the characteristics of the hysteresis loops. The FORCs were processed with the program FORCinel [122] using the VARIFORC method for variable smoothing [123]. The magnetic hysteresis loops show small openings, indicative of a weakly ferromagnetic component present in all the samples (insets Fig.…”

Section: Sample Preparation and Characterisationmentioning

confidence: 99%

Elastic and anelastic relaxation behaviour of perovskite multiferroics I: PbZr0.53Ti0.47O3 (PZT)–PbFe0.5Nb0.5O3 (PFN)

et al. 2016

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Perovskites in the ternary system PbTiO 3 (PT)-PbZrO 3 (PZ)-Pb(Fe 0.5 Nb 0.5 )O 3 (PFN) have attracted close interest because they can display simultaneous ferroelectric, magnetic and ferroelastic properties. Those with the most sensitive response to external fields are likely to have compositions near the morphotropic phase boundary (MPB) which lies close to the binary join Pb(Zr 0.53 Ti 0.47 )O 3 (PZT)-PFN. In the present study, the strength and dynamics of strain coupling behaviour which accompanies the development of ferroelectricity and (anti)ferromagnetism in ceramic PZT-PFN samples have been investigated by resonant ultrasound spectroscopy. Elastic softening ahead of the cubic-tetragonal transition does not fit with models based on dispersion of the soft mode or relaxor characteristics but is attributed, instead, to coupling between acoustic modes and a central peak mode from correlated relaxations and/or microstructure dynamics. Softening of the shear modulus through the transition by up to *50 % fits with the expected pattern for linear/quadratic strain/order parameter coupling at an improper ferroelastic transition and close to tricritical evolution for the order parameter. Superattenuation of acoustic resonances in a temperature interval of *100 K below the transition point is indicative of mobile ferroelastic twin walls. By way of contrast, the first-order tetragonalmonoclinic transition involves only a small change in the shear modulus and is not accompanied by significant changes in acoustic dissipation. The dominant Address correspondence to E-mail: mc43@esc.cam.ac.uk DOI 10.1007/s10853-016-0280-2 J Mater Sci (2016) 51:10727-10760 feature of the elastic and anelastic properties at low temperatures is a concaveup variation of the shear modulus and relatively high loss down to the lowest temperature, which appears to be the signature of materials with substantial local strain heterogeneity and a spectrum of strain relaxation times. No evidence of magnetoelastic coupling has been found, in spite of the samples displaying ferromagnetism below *550 K and possible spin glass ordering below *50 K. For the important multiferroic perovskite ceramics with compositions close to the MPB of ternary PT-PZ-PFN, there must be some focus in future on the role of strain heterogeneity.

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“…2,13 The FORC diagram is confined to the positive half-plane of the coercivity axis because H > H r and therefore H c > 0. Different examples of FORC density distributions will be shown later in Sec.…”

Section: A First-order Reversal Curvesmentioning

confidence: 99%

Application of magneto-optical Kerr effect to first-order reversal curve measurements

Gräfe

Schmidt

Audehm

et al. 2014

Review of Scientific Instruments

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Simple quadratic magneto-optic Kerr effect measurement system using permanent magnets Review of Scientific Instruments 88, 013901 (2017) First-order reversal curves (FORC) are a powerful method for magnetic sample characterization, separating all magnetic states of an investigated system according to their coercivity and internal magnetic interactions. A major drawback of using measurement techniques like VSM or SQUID, typically applied for FORC acquisition, is the long measurement time, limiting the resolution and the number of measurements due to time constraints. Faster techniques like MOKE result in problems regarding measurement stability over the curse of the acquisition of many minor loops, due to drift and non-absolute magnetization values. Here, we present an approach using a specialized field shape providing two anchor points for each minor loop for applying the magneto-optical Kerr effect (MOKE) technique to FORC measurements. This results in a high field resolution while keeping the total acquisition time to only a few minutes. MOKE FORC measurements are exemplarily applied to a simple permalloy film, an exchange-bias system, and a Gd/Fe multilayer system with perpendicular magnetic anisotropy, showcasing the versatility of the method. © 2014 AIP Publishing LLC.

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VARIFORC: An optimized protocol for calculating non-regular first-order reversal curve (FORC) diagrams

Cited by 249 publications

References 47 publications

Multiphase magnetic systems: Measurement and simulation

Multiphase magnetic systems: Measurement and simulation

Elastic and anelastic relaxation behaviour of perovskite multiferroics I: PbZr0.53Ti0.47O3 (PZT)–PbFe0.5Nb0.5O3 (PFN)

Application of magneto-optical Kerr effect to first-order reversal curve measurements

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