스핀트로닉스 스핀궤도토크(SOT-MRAM) 스핀 홀 효과 & 1,000Hz 0-Alloc C# 스핀 편극 전류 자화 스위칭 서보 엔진

using System;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

namespace ZeliDesk.Stem.SpintronicsControl
{
    /// <summary>
    /// 3차원 자화 벡터 (정규화 단위 벡터 mx, my, mz)
    /// </summary>
    [StructLayout(LayoutKind.Sequential, Pack = 8)]
    public readonly struct MagnetizationVector
    {
        public readonly double Mx;
        public readonly double My;
        public readonly double Mz; // +1.0: Up (Parallel), -1.0: Down (Anti-Parallel)

        public MagnetizationVector(double mx, double my, double mz)
        {
            Mx = mx; My = my; Mz = mz;
        }
    }

    /// <summary>
    /// SOT 기입 펄스 제어 명령 (스택 할당 0-Alloc)
    /// </summary>
    public ref struct SotPulseCommand
    {
        public double PulseCurrentDensityA_m2;
        public double PulseDurationNs;
        public bool InPlaneBiasAssisted;
        public bool SwitchingVerified;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public SotPulseCommand(double jc, double durationNs, bool biasAssist, bool verified)
        {
            PulseCurrentDensityA_m2 = jc;
            PulseDurationNs = durationNs;
            InPlaneBiasAssisted = biasAssist;
            SwitchingVerified = verified;
        }
    }

    /// <summary>
    /// 1,000Hz 무할당 SOT-MRAM 스위칭 제어 서보 엔진
    /// </summary>
    public ref struct SotMramSwitchingEngine
    {
        private const double SpinHallAngle = 0.35; // Beta-W 스핀 홀 각도
        private const double SaturationMagnetization = 1.2e6; // A/m (CoFeB)
        private const double FreeLayerThicknessM = 1.2e-9; // 1.2 nm
        private const double AnisotropyFieldA_m = 3.5e5; // A/m (Hk)
        private const double PlanarBiasFieldA_m = 4.0e4; // A/m (Hx)
        private const double HbarOver2e = 5.272859e-16; // J*s / C

        private double _accumulatedWriteEnergy;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public void ExecuteSwitchingCycle(
            in MagnetizationVector currentMag,
            bool targetStateUp,
            double ambientTemperatureK,
            out SotPulseCommand command,
            out double criticalCurrentDensity)
        {
            // 1. 임계 스위칭 전류 밀도 계산 (Jc0)
            double effectiveH = Math.Max(0.1 * AnisotropyFieldA_m, 0.5 * AnisotropyFieldA_m - PlanarBiasFieldA_m / 1.41421356);
            criticalCurrentDensity = (SaturationMagnetization * FreeLayerThicknessM * effectiveH) / (HbarOver2e * SpinHallAngle * 1e18);

            // 2. 현재 상태와 목표 상태 비교
            bool currentStateUp = currentMag.Mz > 0.0;
            bool needSwitch = currentStateUp != targetStateUp;

            if (!needSwitch)
            {
                command = new SotPulseCommand(0.0, 0.0, false, true);
                return;
            }

            // 3. 온도 보상 인자 (열 활성화에 의한 임계 전류 감소 모델)
            double tempFactor = Math.Max(0.6, 1.0 - (ambientTemperatureK - 300.0) * 0.0015);
            double appliedJc = criticalCurrentDensity * 1.25 * tempFactor; // 25% 오버드라이브 마진

            // 반전 방향에 따른 전류 부호 결정 (+: Down->Up, -: Up->Down)
            if (!targetStateUp)
            {
                appliedJc = -appliedJc;
            }

            double pulseNs = 1.5; // 1.5 ns 초고속 스위칭
            _accumulatedWriteEnergy += Math.Pow(appliedJc, 2.0) * pulseNs * 1e-9;

            command = new SotPulseCommand(appliedJc, pulseNs, true, false);
        }
    }
}