FeNiBilayerBuilder.cpp

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//  ************************************************************************************************
//
//  BornAgain: simulate and fit reflection and scattering
//
//! @file      Sample/StandardSamples/FeNiBilayerBuilder.cpp
//! @brief     Defines various sample builder classes to
//!            test polarized specular computations
//!
//! @homepage  http://www.bornagainproject.org
//! @license   GNU General Public License v3 or higher (see COPYING)
//! @copyright Forschungszentrum Jülich GmbH 2020
//! @authors   Scientific Computing Group at MLZ (see CITATION, AUTHORS)
//
//  ************************************************************************************************
 
#include "Sample/StandardSamples/FeNiBilayerBuilder.h"
#include "Base/Const/PhysicalConstants.h"
#include "Base/Const/Units.h"
#include "Sample/Material/MaterialFactoryFuncs.h"
#include "Sample/Multilayer/Layer.h"
#include "Sample/Multilayer/MultiLayer.h"
#include "Sample/Slice/LayerRoughness.h"
 
namespace {
auto constexpr rhoMconst = -PhysConsts::m_n * PhysConsts::g_factor_n * PhysConsts::mu_N
                           / PhysConsts::h_bar / PhysConsts::h_bar * 1e-27;
 
class Options {
public:
    int _NBilayers = 4;
    double _angle = 0.;
    double _magnetizationMagnitude = 1.e7;
    double _thicknessFe = 100. * Units::angstrom;
    double _thicknessNi = 40. * Units::angstrom;
    double _sigmaRoughness = 0.;
    int _effectiveSLD = 0;
    RoughnessModel _roughnessModel = RoughnessModel::TANH;
 
    Options() {}
    Options NBilayers(int n)
    {
        _NBilayers = n;
        return *this;
    }
    Options angle(double angle)
    {
        _angle = angle;
        return *this;
    }
    Options magnetizationMagnitude(double M)
    {
        _magnetizationMagnitude = M;
        return *this;
    }
    Options thicknessFe(double t)
    {
        _thicknessFe = t;
        return *this;
    }
    Options thicknessNi(double t)
    {
        _thicknessNi = t;
        return *this;
    }
    Options sigmaRoughness(double r)
    {
        _sigmaRoughness = r;
        return *this;
    }
    Options effectiveSLD(int i)
    {
        _effectiveSLD = i;
        return *this;
    }
    Options roughnessModel(RoughnessModel rm)
    {
        _roughnessModel = rm;
        return *this;
    }
};
//! Creates the sample demonstrating an Fe-Ni Bilayer with and without roughness
//! @ingroup standard_samples
class FeNiBilayer {
public:
    FeNiBilayer(Options opt = {})
        : NBilayers(opt._NBilayers)
        , angle(opt._angle)
        , magnetizationMagnitude(opt._magnetizationMagnitude)
        , thicknessFe(opt._thicknessFe)
        , thicknessNi(opt._thicknessNi)
        , sigmaRoughness(opt._sigmaRoughness)
        , effectiveSLD(opt._effectiveSLD)
        , roughnessModel(opt._roughnessModel)
    {
        if (angle != 0. && effectiveSLD != 0.)
            throw std::runtime_error("Cannot perform scalar computation "
                                     "for non-colinear magnetization");
 
        magnetizationVector = kvector_t(magnetizationMagnitude * std::sin(angle),
                                        magnetizationMagnitude * std::cos(angle), 0);
        sample = constructSample();
    }
 
    MultiLayer* release() { return sample.release(); }
 
private:
    static constexpr auto sldFe = complex_t{8.02e-06, 0};
    static constexpr auto sldAu = complex_t{4.6665e-6, 0};
    static constexpr auto sldNi = complex_t{9.4245e-06, 0};
 
    int NBilayers;
    double angle;
    double magnetizationMagnitude;
    double thicknessFe;
    double thicknessNi;
    double sigmaRoughness;
    int effectiveSLD;
    RoughnessModel roughnessModel;
 
    kvector_t magnetizationVector;
 
    std::unique_ptr<MultiLayer> sample;
 
    std::unique_ptr<MultiLayer> constructSample();
};
 
} // namespace
 
const complex_t FeNiBilayer::sldFe;
const complex_t FeNiBilayer::sldAu;
const complex_t FeNiBilayer::sldNi;
 
std::unique_ptr<MultiLayer> FeNiBilayer::constructSample()
{
    auto sample = std::make_unique<MultiLayer>();
 
    auto m_ambient = MaterialBySLD("Ambient", 0.0, 0.0);
    auto m_Fe =
        effectiveSLD == 0
            ? MaterialBySLD("Fe", sldFe.real(), sldFe.imag(), magnetizationVector)
            : MaterialBySLD("Fe", sldFe.real() + effectiveSLD * rhoMconst * magnetizationMagnitude,
                            sldFe.imag(), kvector_t{0, 0, 0});
 
    auto m_Ni = MaterialBySLD("Ni", sldNi.real(), sldNi.imag());
    auto m_Substrate = MaterialBySLD("Au", sldAu.real(), sldAu.imag());
 
    Layer l_Fe{m_Fe, thicknessFe};
    Layer l_Ni{m_Ni, thicknessNi};
 
    LayerRoughness roughness{sigmaRoughness, 0., 0.};
    sample->addLayer(Layer{m_ambient});
 
    for (auto i = 0; i < NBilayers; ++i) {
        sample->addLayerWithTopRoughness(l_Fe, roughness);
        sample->addLayerWithTopRoughness(l_Ni, roughness);
    }
 
    sample->addLayerWithTopRoughness(Layer{m_Substrate}, roughness);
    sample->setRoughnessModel(roughnessModel);
    return sample;
}
 
MultiLayer* FeNiBilayerBuilder::buildSample() const
{
    auto sample = FeNiBilayer{Options()};
    return sample.release();
}
 
MultiLayer* FeNiBilayerTanhBuilder::buildSample() const
{
    auto sample = FeNiBilayer{
        Options().sigmaRoughness(2. * Units::angstrom).roughnessModel(RoughnessModel::TANH)};
    return sample.release();
}
 
MultiLayer* FeNiBilayerNCBuilder::buildSample() const
{
    auto sample = FeNiBilayer{
        Options().sigmaRoughness(2. * Units::angstrom).roughnessModel(RoughnessModel::NEVOT_CROCE)};
    return sample.release();
}
 
MultiLayer* FeNiBilayerSpinFlipBuilder::buildSample() const
{
    auto sample = FeNiBilayer{Options().angle(38. * Units::deg)};
    return sample.release();
}
 
MultiLayer* FeNiBilayerSpinFlipTanhBuilder::buildSample() const
{
    auto sample = FeNiBilayer{Options()
                                  .angle(38 * Units::deg)
                                  .sigmaRoughness(2. * Units::angstrom)
                                  .roughnessModel(RoughnessModel::TANH)};
    return sample.release();
}
 
MultiLayer* FeNiBilayerSpinFlipNCBuilder::buildSample() const
{
    auto sample = FeNiBilayer{Options()
                                  .angle(38 * Units::deg)
                                  .sigmaRoughness(2. * Units::angstrom)
                                  .roughnessModel(RoughnessModel::NEVOT_CROCE)};
    return sample.release();
}