# Analysis of High-Field-Induced Processes with Enthalpy Release in Martensite–Austenite MnCo(Fe)(GeSi) Alloys: Solving PPMS Artifact and Recovery of Heat Capacity

## TL;DR

This paper explains how to correct heat capacity measurements in magnetic alloys using a new method that accounts for subtle enthalpy changes during phase transitions.

## Contribution

A new procedure is introduced to correct PPMS data by modeling subtle enthalpy contributions during phase transitions.

## Key findings

- A high-magnetic-field-induced transformation was detected with a subtle enthalpy contribution.
- A new method was developed to recover heat capacity data and estimate enthalpy changes.
- The procedure was successfully applied to MnCo(Fe)Ge(Si) alloys.

## Abstract

What are the main findings?
Analysis of an apparent anomaly detected by PPMS and reinterpretation of results.High-magnetic-field-induced transformation was detected, implying a subtle enthalpy (ΔH) contribution.Recovery of heat capacity data and estimation of ΔH.

Analysis of an apparent anomaly detected by PPMS and reinterpretation of results.

High-magnetic-field-induced transformation was detected, implying a subtle enthalpy (ΔH) contribution.

Recovery of heat capacity data and estimation of ΔH.

What are the implications of the main findings?
Modeling ΔH contribution during data acquisition yields physically sound results.Good interpretation of measurements allows for estimation of ΔH contributions.Checking the conductance of wires for good behavior is needed.

Modeling ΔH contribution during data acquisition yields physically sound results.

Good interpretation of measurements allows for estimation of ΔH contributions.

Checking the conductance of wires for good behavior is needed.

The relaxation calorimeter option in the commercial Physical Property Measurement System (PPMS) has become widely used. Since its introduction, the capabilities of this technique for specific heat measurements have been critically discussed, particularly to avoid misinterpretation of data near phase transitions. Traditional methods rely on cooling curves after sample excitation, where sharp latent heat contributions during heating lead to clear deviations from the fitting model. However, subtle but extended enthalpy contributions (e.g., strain release) may mask these effects, allowing both heating and cooling curves to be well fitted using the standard PPMS protocol. In this work, we develop a procedure that assumes a constant extra power supplied due to subtle enthalpy contributions, enabling consistent interpretation of both heating and cooling curves. This procedure allows: (1) correction of specific heat measurements; and (2) quantification of the enthalpy involved in the transition. The procedure is applied to a magnetic-field-induced transformation in MnCo(Fe)Ge(Si) alloys. Two samples were studied: a single-phase austenite without any field-induced transition, used as a reference, and a mixed austenite-martensite sample, in which apparent deviations in the conductance of the wires evidence the presence of the anomaly.