TimeAsymmetric FORC diagrams Distinguishing magnetic phases based on

Time-Asymmetric FORC diagrams Distinguishing magnetic phases based on their viscosity http: //etc. ch/mx. DG Thomas A. Berndt, Shishun Wang, Liao Chang Peking University https: //directpoll. com/r? XDbz. PBd 3 ix. Yqg 8 o. Fke. WLa. Q 9 JKt. ZEkv. Tzm. Es 5 UAUB

Disclaimer As I have been working in a “real job” last year following my graduation, and only been back in science since October 2017 (at Peking University), the following is a work in progress and contains (almost) no real data, but only theory and simulations. http: //etc. ch/mx. DG

Quiz 1 (warm-up) http: //etc. ch/mx. DG What feature is most prominent in this FORC diagram? a. b. c. d. single-domain (SD) grains multi-domain (MD) grains interactions I don’t know what a FORC diagram is

Quiz 2 http: //etc. ch/mx. DG What feature is most prominent in this FORC diagram? a. b. c. d. e. single-domain (SD) grains multi-domain (MD) grains interactions thermal fluctuations multiple magnetic phases

Quiz 3 http: //etc. ch/mx. DG What feature is most prominent in this FORC diagram? a. b. c. d. e. single-domain (SD) grains multi-domain (MD) grains interactions thermal fluctuations multiple magnetic phases

First-order reversal curves (FORC) Roberts et al. (2000)

First-order reversal curves (FORC) Roberts et al. (2000)

First-order reversal curves (FORC) Roberts et al. (2014)

First-order reversal curves (FORC) Roberts et al. (2014)

First-order reversal curves (FORC) Coordinate transformation

Preisach theory Roberts et al. (2014)

Preisach theory Roberts et al. (2014)

Non-interacting single-domain grains

Thermal fluctuation field

Thermal fluctuation field Thermal fluctuations are a gradual statistical process!

Simulated FORCs with thermal fluctuations Magnetite Titanomagnetite Both

1 st result Thermal fluctuations cause a vertical spread in FORC diagrams, similar to interactions.

Time-asymmetric FORCs

Simulated time-asymmetric FORCs Magnetite

Simulated time-asymmetric FORCs Titanomagnetite

2 nd result •

Simulated time-asymmetric FORCs Mixture of Magnetite + Titanomagnetite

3 rd result Time-asymmetric FORC diagrams can help to separate magnetic phases that overlap completely in conventional FORC diagrams.

Why does the viscosity differ? •

Mixtures of minerals TS-FORC TA-FORC Magnetite Titanomagnetite Both

Mixtures of grain shapes TS-FORC TA-FORC Needles Spheres Both

4 th result Both magnetic minerals and grain shapes can be separated due to their different viscosities.

Extra: Preliminary experimental data (Thanks to Shishun Wang and Liao Chang) Time-symmetric

Extra: Preliminary experimental data (Thanks to Shishun Wang and Liao Chang) Time-asymmetric