Induced-Moment Exchange Explorer

Bring an UppASD input set into the explorer

Upload inpsd.dat and its referenced files. The inpsd.dat file is required because it supplies the explicit cell vectors used for reciprocal-space analysis; individual posfile, momfile, and jfile uploads alone are not loaded and no identity cell is assumed. If inpsd.dat contains alat (in metres), the loader applies it automatically to the cell, positions, and exchange displacements. References are matched by basename because browser uploads do not preserve arbitrary relative paths; manual assignment is available below.

Raw rigid-site exchange

All supplied sites and literal UppASD jfile Jij rows are retained. The ordering diagnostic is the largest eigenvalue of J(q) under the UppASD ordered-pair convention H = −Σᵢ≠ⱼ Jij eᵢ·eⱼ. The scan is restricted to the seekpath high-symmetry path (or the explicitly labelled fallback path if seekpath cannot classify the structure); it is not a global 3-D ordering search. The distance plot separates J_MM (robust–robust, circles), J_Mm (robust–induced, squares), and J_mm (induced–induced, triangles).

Load an input set and run analysis.

Induced response

Classify sites explicitly in the Input tab. The induced response is algebraic and instantaneous; induced sites are not independent LLG/LSWT degrees of freedom. The response panel uses a coherent unit-amplitude robust spin spiral along the same seekpath high-symmetry path.

Robust-space exchange after induced-moment elimination

The induced contribution is a model-dependent correction using the selected response approximation. J_eff(q) is the Fourier-space matrix in the robust basis; the q-plot shows its leading eigenvalue. For one robust site (such as Fe with Pt treated as induced), this matrix is a scalar. The first real-space plot uses shell means to compare the direct J_RR(r), cross-block K_RI(r), Mryasov/downfolded J_Mryasov(r), and Polesya-like induced J_Polesya(r) channels. With the same static response model, the last two are numerically equivalent and are shown with separate labels. The induced correction ΔJ_induced(r) and its relative value ΔJ_induced(r) / J_RR(r) are plotted separately below. Real-space x-axes use the implicit UppASD lattice parameter convention (alat = 1), while all curves are reconstructed from a separate complete q mesh; moment normalization remains separate in the magnon calculation. The exported dressed_jfile is directly compatible with UppASD's ordered-pair convention.

FM-compatible spectra

If Gamma is not locally stable, the plot is explicitly signed harmonic data, not a stable magnon spectrum.

Compare two compatible Jij datasets

Useful for LKAG vs frozen-magnon comparisons. Basis cell/positions must match; exchange values are allowed to differ.

Methods in one page

Raw rigid-site model. Every supplied magnetic site is treated as an ordinary rigid moment. This is diagnostic when some sites are physically induced.

Polesya-like induced moments. Induced moments are eliminated as algebraic variables. The historical mode uses an unweighted local neighbour sum; the selected J-weighted mode evaluates the labelled J-weighted induced-response approximation.

Mryasov-like downfolding. The induced subspace is eliminated variationally from one quadratic energy functional, yielding a robust-space J_eff(q). No induced magnon branches are added.

Reciprocal sampling. The exchange, response, dressed-exchange, and magnon plots share a seekpath high-symmetry path. The dressed real-space channel, absolute-correction, and relative-correction plots are reconstructed from a separate complete auxiliary mesh and are not inferred from that line.

Important limitation. Conventional input Jij are not, by themselves, an exact first-principles susceptibility or induction kernel. Results depend on the explicit classification, X values, response mode, and conditioning of I − X K_II.

The conceptual foundations are discussed in Mryasov et al. on induced moments and two-ion anisotropy in FePt, and Polesya et al. on induced moments in FePd/CoPt. See the repository README for the scope and citations. Unsupported cases are flagged rather than silently converted: noncollinear order, AF/ferrimagnetic LSWT, DMI, exchange tensors, SOC, anisotropy, and frequency-dependent susceptibility.